6. Understanding Old Tank Syndrome
Understanding Old Tank Syndrome Old Tank Syndrome: When Neglect Catches Up Now, what about tanks that have been running for years? This brings us to the dreaded Old Tank Syndrome—a term advanced aquarists use to describe an aging aquarium that’s showing signs of ecosystem failure. But wait! Isn’t a mature tank supposed to be stable? Yes! However, old tank syndrome isn’t an inevitable problem—it’s a result of neglected maintenance over time. Without proper care, even a well-established tank can experience a slow breakdown. Warning Signs of Old Tank Syndrome: Plummeting pH levels – Acidification from organic waste buildup. Uncontrolled algae growth – A sign of nutrient imbalance. Excessive nitrate accumulation – The tank can’t keep up with waste processing. Sluggish biological activity – Reduced efficiency in breaking down waste. And the main culprit? The substrate (gravel, sand, or soil) at the bottom of your tank. Why Your Substrate Matters Over time, the substrate becomes a dumping ground for organic waste, detritus, and grime. If left unmanaged, this build-up can choke your ecosystem and throw your tank out of balance. But don’t worry! You can prevent old tank syndrome with these simple maintenance habits: How to Keep an Old Tank Healthy: ✅ Use sludge-eating bacteria – These special bacteria break down organic waste in the substrate. Available in liquid form at most of our stores. ✅ Gentle Cleaning – When doing water changes, lightly wave your hand around plants and decorations to dislodge trapped debris before siphoning it out. ✅ Siphon Your Substrate – Use a gravel vacuum to remove excess detritus from the substrate. This prevents nutrient overload. https://thataquarium.com/wp-content/uploads/2025/04/gravel-vacuumm-1.mp4 ✅ Don’t Clean Everything at Once! – Never wash your filter and deep-clean your substrate on the same day. Your beneficial bacteria need stability! ✅ Trim & Maintain Plants – Aquarium plants trap detritus. Keep them trimmed and fertilized so they compete with nuisance algae rather than harboring excess waste. ✅ Monitor Water Quality – If pH is dropping, add KH buffer to stabilize it. A little goes a long way, so don’t overdo it. ✅ Stock Sensibly – Avoid overstocking! It’s tempting to add more fish as your old tank ages, but resist the urge. Understocking is always better than overstocking. Final Thoughts: Balance Takes Time Whether it’s a new tank or an old one, balance doesn’t happen overnight. The key to a healthy aquarium is gradual, consistent care. Take things slow. Let your ecosystem develop naturally, and in return, your fish will thrive. Avoid stress—for both you and your fish! Got questions? Drop by our store for expert advice and free water testing. Let’s make your aquarium a success, one step at a time! Happy Fishkeeping! 🐠🌱 👉 Next Up: Aquarium Placement 🐡 Puffed up with knowledge? Give us a like and keep floating along! Proudly presented by our That Aquarium Digital Team, where innovation meets aquatic excellence. Author: Kelvin Phua Illustrator(s): Chai Minyu, Abbie Tan
5. Understanding New Tank Syndrome
Understanding New Tank Syndrome 3 min New Tank Syndrome: Why Patience is Key Wow! You’ve made it this far, and now, defining ‘new tank syndrome’ is a breeze. Simply put, it refers to a newly set-up aquarium that hasn’t yet established its nitrogen cycle. Without this cycle in place, the tank lacks biological stability and is far from achieving equilibrium. Recap: Why is This Important? In a new tank, ammonia (NH3) and nitrite (NO2) are present, which means the nitrogen cycle hasn’t fully developed yet. Both of these compounds are highly toxic to fish and must be at 0ppm before adding livestock. If ammonia and nitrite levels are detected in your water tests, it means your tank isn’t ready yet. This is why patience is key—rushing the process can lead to stressed or even dying fish. So, what’s the big deal? A new tank is like a blank slate—it needs time for beneficial bacteria to grow and take charge of waste management. Your job? Give your bio-filtration system a head start and allow the ecosystem to settle before adding too many fish. Here’s the golden rule: Take it slow. Avoid impulse buying new fish after setting up your tank. Instead, focus on creating a stable environment. When you take care of your aquarium, it will take care of your fish in return. It’s really that simple! 👉 Next Up: We’ll explore old tank syndrome — and the signs you should look out for. 🐡 Puffed up with knowledge? Give us a like and keep floating along! Proudly presented by our That Aquarium Digital Team, where innovation meets aquatic excellence. Published on 13 June 2025 Author: Kelvin Phua Illustrator(s): Chai Minyu, Abbie Tan
4. The Nitrogen Cycle
4. The Nitrogen Cycle What is the nitrogen cycle, and why is it important? Congratulations on making it this far in our beginner’s guide to aquatic ecosystems! From here on, we’ll briefly recap key topics covered in earlier sections. Yes, that’s right! We’ve been gradually introducing the nitrogen cycle throughout this guide, making it easier to grasp. So, at this stage, you may notice some familiar concepts rather than entirely new and complex information. As a bonus, we’ll also share helpful aquarium husbandry tips along the way. So, let’s dive in! Ammonia Production Let’s quickly go over ammonia (NH3) again. It’s an inorganic waste compound produced when organic waste materials break down, primarily due to heterotrophic bacteria. At high concentrations, ammonia is toxic to aquatic life, which is why a stable nitrogen cycle is crucial for maintaining a healthy aquarium. This process is supported by an efficient filtration system. Now, you may already know that fish waste contributes to ammonia buildup, but did you know that there are other invisible sources of nitrogenous waste? Let’s explore a few: 1. Nitrogen-fixing bacteria Surprise! Alongside your beneficial nitrifying bacteria, another group of bacteria exists—one that actually increases the ammonia load in your aquarium. These nitrogen-fixing bacteria take atmospheric nitrogen and convert it into ammonia. Why? It’s simply part of nature’s process to make nutrients available to plants. While they thrive in terrestrial soil, they can also appear in aquatic environments. However, if your filtration system maintains optimal conditions for nitrifying bacteria, nitrogen-fixing bacteria will have limited space to establish themselves, keeping their population under control. 2. Dead or Dying plants When plants or their leaves decay—whether due to natural shedding or neglect—they release ammonia and nitrate into the water. This is why we recommend hardy aquarium plants that thrive with minimal upkeep. A well-maintained plant selection reduces decomposition-related water quality issues. Not sure which plants to choose? Our plant hobbyists are always happy to recommend the best species for your aquarium! 3. Overfeeding This one’s a big no-no! Uneaten food rapidly breaks down, releasing ammonia and other harmful compounds into the water. Fish food is rich in proteins, oils, and other ingredients that can severely degrade water quality if left to rot. As a rule of thumb, feed your fish until they appear about 75% full. Remember, in most cases, a fish’s stomach is roughly the same size as its eyeball—so don’t overdo it! 4. Urea (A Special Case) Certain fish species, like stingrays and sharks (elasmobranchs), excrete a concentrated ammonia compound known as urea. If you’re considering keeping freshwater stingrays, you’ll need a powerful filtration system to handle their high bioload. Always research a fish’s care requirements before adding it to your aquarium—especially species with specialized needs. A general rule: the more expensive the fish, the more demanding its care requirements tend to be. Starting with hardy fish will build your confidence and fishkeeping skills before tackling more challenging species. Beneficial Bacteria: The Heart of the Nitrogen Cycle Fish excrete waste in two forms: solid fecal matter (organic) and ammonia (inorganic) through their gills. Here’s how beneficial bacteria manage this waste: Heterotrophic bacteria break down organic waste into ammonia. Nitrosomonas bacteria convert ammonia (NH3) into nitrite (NO2), which is still toxic. Nitrobacter bacteria convert nitrite (NO2) into nitrate (NO3), a much less toxic compound. This process, called nitrification, happens in the presence of oxygen, making it an aerobic process. Denitrification: The Anaerobic Side of the Nitrogen Cycle Did you know that another group of beneficial bacteria can remove excess nitrates from your aquarium without needing oxygen? These are called denitrifying bacteria or anaerobes. Unlike aerobic nitrification, anaerobic denitrification occurs in low-oxygen environments, such as deep substrate layers. Anaerobes thrive in areas where oxygen is scarce, such as within compacted sand beds or deep substrate layers where water circulation is minimal. However, if waste accumulates excessively in these areas, toxic by-products like hydrogen sulfide (H2S) can form, giving off a rotten egg odor. To prevent issues: Keep sand beds no deeper than 5 cm (2 inches). Use live plants—their roots help oxygenate the substrate. Occasionally rake the substrate to release trapped gases. Thus, the way forward toward establishing equilibrium within your aquarium is by managing its nitrogen cycle. Finding harmony between aerobic nitrification and anaerobic denitrification in practice is a lot easier than it seems. All that is required of you can be simplified in just three steps: Establish your aerobic nitrification cycle. Do not overstock, and lastly. Avoid overfeeding. That’s Simple! How To Establish Your Aquarium’s Nitrogen Cycle There are two ways to establish your nitrogen cycle: ‘cycling’ your aquarium. The first method is the natural way. By simply letting your newly set up aquarium run its course for several weeks in the absence of fishes, aerobic nitrifying bacteria will naturally occur in your aquarium. This will be evident as you notice a decline in your aquarium’s ammonia level during water testing, and as the weeks progress, your nitrite levels will rise. Finally, nitrite levels will decline as nitrate levels climb, and this is the indication that your tank has completely cycled and is now ready for fish to be stocked into the aquarium. Under no circumstances should you introduce fish into your tank when ammonia and nitrite levels are detectable. Always cycle your aquarium fully. Tips: To play safe, make sure ammonia and nitrite levels are at 0 ppm. If they are not at this level, reduce feeding, reduce the bioload, and perform more frequent water changes. If you encounter this issue, please bring about 100ml of your aquarium water to our stores. We offer free water testing, and our staff will be happy to guide you step by step to resolve the matter. This can take weeks to slightly over a month, and thus, it brings us to the second method, i.e., the sped-up cycling process. Using the sped-up version of the tank cycling method allows you to establish nitrification almost instantly. This allows fish to be stocked
3. Importance of Water Parameters in Aquarium Maintenance
Introduction Before we delve deeper into the more technical aspects of aquarium maintenance, let’s peek at what makes owning an aquarium of your own a fun and rewarding hobby. Unlike owning a pet cat or dog, which can be cuddled, our finny friends dwelling in an aquarium live in a world of their own, and you are both the creator and custodian of their world! Wow, how cool is that? Uber cool! This is why an aquarist who has learned the ways of fish farming will often mesmerize you with their seemingly “otherworldly” knowledge of the underwater world, but just like you, once upon a time, a familiar aquarist was a beginner, too. This guide is designed to be inclusive, catering to beginners and familiar hobbyists. It’s a resource that makes learning about aquarium maintenance easy and enjoyable for beginners while also offering valuable insights for more experienced hobbyists. Whether you’re just starting out or have some experience keeping fish and/or aquatic plants alive, this guide is for you. Now, let’s dive into the fascinating world of maintaining healthy water parameters in your aquarium, starting with the biological stability of the aquarium. Biological Stability Relax. We promise you this will not be a biology class lecture. The term “biological stability” is trying to tell you that an aquarium is full of life—more than just your fish and plants that you can see! There are all kinds of microscopic critters living in your aquarium, both visible to the naked eye and invisible, and believe it or not, the presence of these microorganisms in your aquarium keeps your fish and plants healthy. So, what are these tiny creatures secretly helping you sustain a healthy aquatic environment in your tank? Beneficial bacteria and archaea are doing the bulk of the hard work for you, and the eukaryotes, aka fungi, support them! These are the invisible “heroes” living in your aquarium (mainly in the aquarium filter and gravel layer), and by providing stable water parameters in your aquarium, they will help to convert toxic fish wastes (excrements of metabolic processes from digestion of food) into less harmful compounds. This helps to maintain good quality water that is liveable for your fish and plants. Interesting. Yet, very often, we’d only hear hobbyists talking about “beneficial bacteria” in the aquarium, but actually, bacteria are part of a more extensive food web that exists in Nature, and this is simply because bacteria for our aquarium use are the easiest to culture for commercial purposes. Yes, you can buy beneficial bacteria at most aquarium stores to seed your aquarium filter, but the real magic happens when these beneficial microorganisms naturally occur in your aquarium. They are Nature’s unsung heroes – a natural clean up crew that we first learnt of through Science, termed as the ‘nitrogen cycle’. Why nitrogen? Well, organic wastes are mostly nitrogenous in their makeup. And the role of beneficial bacteria, as well as archaea and eukaryotes, is to consume nitrogenous wastes as a source of “food”. In the process, they help to render toxic organic wastes into their less toxic form. Lastly, these less toxic wastes are finally reduced to nitrogen gas that dissipates out of the aquarium into the atmosphere. While some of those wastes end up as food for aquarium plants (if any) in your aquarium. Here is an illustration to show you the nitrogen cycle process: Nitrogen Cycle Process Voila! The end product of the nitrogen cycle is nitrogen gas, an inert (non-toxic) gaseous compound. So, how can you, as a beginner, establish a biologically stable, healthy aquarium like the experts do? Simply by following these expert tips: Now, has it become apparent how vital the nitrogen cycle in your aquarium is? But there is no way of sustaining a healthy aquarium without it. The good news is once the biological stability of your aquarium is firmly established, your aquarium requires minimal intervention. An established aquarium is more than just a glass box with fish in it – it is an ecosystem that can support life! And it is this aspect of the aquarium hobby that truly feels very satisfying! No other pet-keeping offers you a chance to create a small world for your beloved pet quite like an aquarium hobby does, where you get to observe an array of natural behaviors in fishes, from their unique quirks to the joy of seeing young fishes being born in your aquarium! The cycle of life and Nature is at arm’s reach in the comfort of your home! Imagine that! From bacteria to a thriving ecosystem filled with healthy, colorful fishes swimming with their young. Every familiar hobbyist was once a beginner, just like you, now. And it did not take them long to master their own aquarium. It just took them LOVE—to never give up and to understand how fish show us their love for us in return when we take care of their needs. Ammonia and Nitrite Toxicity As we discussed earlier, the accumulation of fish metabolic waste products leads to the buildup of ammonia, a toxic compound that is then converted to nitrite (still a toxic compound) via the nitrification process, which harnesses the power of beneficial bacteria. Thus, this begs the question: How do ammonia and nitrite toxicity affect our aquarium inhabitants? Ammonia and nitrite can pose a severe threat to the health of our aquarium inhabitants. Findings indicate that ammonia levels in water at readings between 0.5mg/l and 22.8mg/l and nitrite levels above 0.5mg/l are both deemed toxic to aquatic life. This is not to exclude nitrates that, while the least harmful of the three nitrogenous waste compounds, can still induce health issues in fish if allowed to accumulate at concentrations of 40 mg/l or more. Thus, ammonia nitrite and nitrate toxicity affect the health of our aquarium inhabitants in different ways. Therefore, we must ensure that all three nitrogenous waste compounds do not reach critical levels by ensuring that the aquarium is not overstocked and its
2. Types of Freshwater Aquariums
Introduction Welcome, new aquarists! Your role in this community is vital. In this chapter, we will be introducing to you the types of aquatic habitats that you can set up for your fishes, shrimps and snails but first of all, what is an ‘aquarium’? The etymology of the word ‘aquarium’ comes from the words ‘aqua’ (meaning ‘water’ in Latin) and ‘vivarium’ (meaning ‘place of life’ in Latin). Therefore, the word ‘aquarium’ is a portmanteau which means “a place/habitat for aquatic life to exist.” Alright, fancy introductions aside, the main takeaway from the definition of an ‘aquarium’ is that it must be able to support life. Add water to the picture, and it now becomes apparent that the aquatic world is indeed vastly different from that of our terrestrial world. Underwater life processes take place differently. That is why we introduced this guide with a basic understanding of water chemistry. Now, without further ado let’s take a look at the 9 (10, including a quarantine aquarium) types of commonly encountered freshwater aquariums; as well as the pros and cons of each type. They are: Community Aquarium Nano Aquarium Species – Specific Aquarium Biotope Aquarium Planted Aquarium (Low Tech) Planted Aquarium (High Tech) Paludarium Breeding Aquarium Aquascaped Aquarium Quarantine Aquarium Community Aquarium By definition, a community aquarium also known as a community tank is a display tank which features a collection of various tropical / coldwater fishes that hail from different habitats across the globe and they can be housed together upon meeting a few basic premises. 1. Compatibility Researching the temperament of your chosen species and their natural behavior is essential before heading down to your favorite local fish store for a procurement. Certain species of fishes are docile and should only be kept with conspecifics of similar temperament, e.g., cardinal tetras, and harlequin rasboras will school together in peace. More boisterous types of fish, such as tiger barbs, for example, are better off housed with, say, a small school of clown loaches or other medium-sized barbs that can reach up to 20 cm in total length when fully matured, despite the tiger barb’s relatively diminutive size of only 5 cm in total length. Another aspect of compatibility concerns the predatory nature of a species – even supposedly “peaceful” species. For example, while a collection of neon tetras and fully grown adult angelfish may seem to evoke an idyllic, tranquil Amazonian river-inspired community, in reality, angelfish will gladly hunt down a neon tetra, shrimp or other similarly built, small fish species that can fit its mouth. Always research a fish’s behavior well. The internet or, better yet, a well-written book on aquarium fish husbandry will often provide vital information you can use as a guideline for deciding your next purchase. While aquarium store staff can also be a source of valuable information for a more in-depth point of reference, nothing proves more dependable than a good quality book, which you can also add to your archives for future reference and inspiration. Moving forward, That Aquarium will also share our experience through this website, Learning Community, to guide you through the aquarium-keeping journey. Stay tune for our update! 2. Water Requirements Do the fish species you intend to combine share a similar pH and GH range? Remember, if you cannot meet all of the fish species’ water parameter requirements, your aquariums will not be able to house your intended mix of fish. For instance, guppies prefer hard water with an alkaline pH, and thus, combining them with a fish species that demands soft, acidic water, such as wild-caught discus fish, will prove detrimental to the latter species. Also, does their preferred water temperature range match? Discus fish, for example, are tropical fish by nature. Keeping them at lower (tropical) temperatures in a planted tank aquarium is not advisable since their physiological needs differ from those of coldwater fishes. Yes, Discus may survive in cold temperatures. Still, for optimal health and vitality, it must be housed in an aquarium, a community tank with water temperatures above 27°C. 3. Dietary Requirements In a community setting, providing a varied and well-balanced diet to the tank’s inhabitants is vital to survival. Most fishes are omnivores that will take a wide variety of dry and live/frozen food items. What is important to note, however, is to ensure that one more of your tank inhabitants are not being deprived of food due to faster or more aggressive fishes hoovering up their share. This also correlates to a fish’s natural feeding mode, e.g., certain species, such as catfishes, are nocturnal in habit. Thus, during daylight hours, the fish may shy away from food, necessitating the addition of food to feast on at night. Once again, researching your intended tankmates’ dietary habits is paramount in ensuring a successful and thriving community aquarium. 4. Size Nothing can feel more debilitating for the new aquarist than seeing an otherwise peaceful fish species outgrow its home in such a short time. Such is the case when the common pleco, which can reach a whopping 60 cm in total length when fully grown, can be seen stressing its smaller tankmates with a swipe of its extensive, armored tail. Alas, the general rule of stocking community aquariums to adhere to would be to house no more than one inch of fish body length per gallon and, ideally, an aquarium at least ten times the fish’s body length. Granted, a single adult Oscar cichlid at 30 cm long can be housed comfortably in a 90 cm long tank, but it must be the only tank inhabitant. More water volume equals more stable water parameters, and more tank space equals less stress, which means you enjoy viewing more of your fish’s natural pinnacle of enjoyment in this hobby! So, dispel all misconceptions you may have heard about how aquarium fishes would supposedly never outgrow their tank size- that is a myth. A fish’s cells are constantly replicating, which not only accounts for its regenerative properties, i.e.,
1. Basics of Freshwater Ecosystems
3 mins Introduction Welcome to the fascinating and wonderful world of aquariums and fish keeping! Here, at That Aquarium we aspire to embark on this journey together with you via this virtual guide; offering both guidelines for the new hobbyists, as well as juicy tidbits of information for the more advanced aquarists. We hope that you will have fun navigating our website and be enthralled by the charm of the aquarium hobby which has captivated many from all walks of life. So, come with us, as we help to guide you towards success with our team of expert aquarists who are just a click away, always by your side! Mother Nature “To Know Mother Nature is to love her smallest creations’’. -Takashi Amano No true words have been spoken other than those of the Mr. Takashi Amano, Nature photographer and founder of the Nature Aquarium style of planted aquariums which took the world by storm. Mother nature is both mysterious and magnanimous. And in our setting up an aquarium, inevitably we are re-creating a small slice of Nature within a glass box. Along with the various natural processes vital for sustaining life, as Nature intended. Thus, let us explore Mother Nature and learn from Her. Beginning with the element that brings life-water. Water. Scientifically classed as the compound known as H2O and also dubbed as the “element” that brings life “across cultures, water exists in Nature as part of the water cycle. Where it is continuously purified and made available for sustaining organic life; both terrestrial and aquatic. A staggering 97% of the Earth’s water makes up the ocean, where it covers more than 70% of our planet’s surface. With the remaining 3% of that water being freshwater. The latter is characterised by lakes, rivers and streams, among others and it is in these types of freshwater habitats do our beloved tropical aquarium fishes abound, as well as their less well-represented coldwater congeners (e.g. sticklebacks and bitterings). Water Cycle By understanding the water cycle, as it happens in Nature we will also learn of how each process alters the physical state and chemical composition of water. For it is the final end product that ends up in our aquariums and thus, the water chemistry of various municipal water supplies may be ideal for certain species of aquariums fishes but not for others. Firstly, water evaporates into the air from open bodies of water i.e. ‘collection points’. Water in its gaseous state is pure H2O and thus free from dissolved compounds. As it rises into the atmosphere to form clouds, however the water will inevitably become slightly acidic. This is due to the presence of Co2 in the air which naturally dissolves into the water to form carbonic acid. This natural process is not to be confused with acid rain brought upon by the dissolution of toxic air pollutants such as sulphur dioxide and nitrogen oxides; which turns the water excessively acidic that can harm both terrestrial and aquatic life. It is here that we derive the first measurable water parameter, pH. Which indicates how acidic (< pH 7.0) or alkaline (> pH 7.0) water can be. Science Time: Water pH stands for “potential of Hydrogen” or “power of Hydrogen.” It is a measure of the hydrogen ion concentration in water, indicating its acidity or alkalinity. The pH scale ranges from 0 to 14. Water Bodies Secondly, as clouds get heavier from continuous condensation of water vapour the resulting water precipitates as rainfall. Depending on where rainwater falls the topography of the ground below will once again after its chemical composition. When water flows over mountainous terrain, especially karst topography its innate carbonic acid will dissolve the overlying calcareous surface; the water, now enriched with calcium carbonate, takes on alkaline pH 7.2-8.5. Examples of freshwater habitats with alkaline water are : Lake Malawi and Lake Tanganyika in East Africa (home to beautiful, dazzling Rift Valley Cichlid species that are popularly kept in home aquariums), as well as many rivers in temperate regions (Europe and North America). What are GH and KH? General Hardness (GH) The presence of dissolved carbonates in the water also gives us yet another important measurable water parameter; hardness levels. Before we delve deeper, understand that water hardness is expressed in two terms; GH and KH. What are GH and KH? GH stands for general hardness while KH stands for carbonate hardness. When calcareous materials e.g. limestone dissolves in water, calcium ions, magnesium ions, carbonates and bicarbonates the water is no longer pure H2O and now becomes ‘hard’ due to the four minerals it has now accumulated. GH is a measure of calcium and magnesium ions while KH is the measure of carbonates and bicarbonates. Confusing? Fret not! Things will only get easier to understand from here. When hobbyists say “My water is hard” they are implying that the GH levels are high. Conversely if the water here is “soft” it means that the GH levels are low. As simple as that! In reality, there are 4 measurable levels of GH (see diagram 2). Namely soft, moderate, hard and very hard. Why do GH levels matter? In Nature, fishes have evolved to adapt to not only specific pH ranges but also a specific GH range too. For example, if we were to rear a sensitive acidophilic (acid water loving) fish such as the liquorice gourami (Parosphromenus spp.) that hail from soft, acidic peat swamps in ordinary tap water with even moderated GH levels the fish will succumb to health issues that will quickly lead to its untimely demise. Thus, the importance of understanding GH levels. Carbonate Hardness (KH) KH is concerned with the water’s buffering capacity aka its ability to help maintain stable pH levels. Are you beginning to see how KH and pH are intertwined, now? That’s great! As mentioned earlier, KH measures the concentration of carbonates and bicarbonates in the water. These 2 compounds are important since they act as buffers to prevent the pH