In this episode of The Aquarist’s Edge, Art explores why minerals are essential for a healthy freshwater aquarium. From GH and KH to pH stability, fish health, shrimp moulting, snail shell development, and aquarium plant growth, you’ll learn how dissolved minerals quietly shape the success of your tank. Whether you use tap water, RO water, or a planted aquarium setup, this episode will help you understand what your water is really doing.
We also explain why clear water is not always healthy water, why chasing pH can cause problems, and how to create stable, suitable water for your fish and plants.
[00:00:00] Welcome to this episode of The Aquarist's Edge, a podcast for home aquarists just like you. Learn more about how to keep a thriving aquarium and discover ideas and tips to give your aquarium the edge. And now over to our host, Arthur Preston. Hi everybody, welcome back to The Aquarist Edge. Today we're going to talk about something you cannot see in your aquarium.
[00:00:24] But your fish, your plants, your snails, shrimp and beneficial bacteria all depend on it. And that is minerals. When people think about water quality, they usually think about ammonia, nitrite, nitrate and pH. Those are important, but they're really not the full story. Because your aquarium water also contains dissolved minerals. And those minerals help determine whether your tank is stable, healthy and suitable for the livestock inside it.
[00:00:52] Clear water is not always healthy water because a tank can look beautiful and still have the wrong mineral balance. So in this episode, I'm going to explain what minerals do, why GH and KH matter, how minerals support fish and plants, and how to avoid some common mistakes. Let's start right at the very basic element here, and that is the water. You know, when we say water, we often imagine pure H2O. But aquarium water is never just H2O.
[00:01:19] It contains dissolved minerals such as calcium, magnesium, potassium, sodium, bicarbonates, carbonates, iron and trace elements. Some of these come from your tap water. Some will come from rocks and substrates, fertilizers, fish food and water conditioners. And others may come from remineralizers if you use Oro water. Now, these minerals are important because fish live completely surrounded by water.
[00:01:45] They're not only swimming in it, they're constantly interacting with it through their gills, their skin and their internal body systems. And that means that the chemistry of the water directly affects their health. A fish that is kept in suitable, stable water does not have to work as hard to stay balanced. A fish kept in unstable or unsuitable water may become stressed even if ammonia and nitrite are zero. Now, the first mineral measurement that aquarists need to understand is GH, or general hardness.
[00:02:14] GH mostly measures calcium and magnesium in the water. These minerals are important for fish health. They help with nerve function, muscle function, bone and scale development, and a process called osmoregulation, which is a nice big fishy science term that simply means it's the way fish balance water and minerals inside their bodies. Freshwater fish are constantly taking in water from their environment, and their bodies must regulate salts and minerals carefully. If the water is too far outside their preferred range, they need to use more energy just to stay balanced.
[00:02:45] Now, that doesn't mean all fish need hard water. Some fish naturally come from soft water, while others prefer harder, more mineral-rich water. Guppies, platys, mollies and many rainbow fish usually appreciate harder water, while many tetras, rasboras and dwarf cichlids often prefer softer water. The key is not whether softer hard water is better. The key is whether your water suits the fish that you're keeping. GH also matters for snails and shrimp, because snails use minerals, especially calcium, to maintain strong shells,
[00:03:13] and shrimp need the right mineral balance for healthy malting. If you use aurel water, distilled water or very soft tap water, your GH may be too low unless you add minerals back. The second key measurement is KH, or carbonate hardness, and this tells us how much buffering capacity the water has. In simple terms, KH helps to keep pH stable. Aquariums naturally produce acid over time.
[00:03:39] Through fish waste, uneaten food, decayed plant material, and the massogen cycle, that all contribute to the addition of acid. If your KH is too low, those acids can cause the pH to drop. Now, well, sometimes this will happen slowly, but sometimes it happens quickly, which we will often call a pH crash. And this can be very stressful for fish. And this is why chasing pH with quick-fix chemicals is usually a bad idea. If your KH is low, your pH may keep moving.
[00:04:08] If your KH is high, your pH may resist change. So instead of asking how do I force my pH down or how do I force my pH up, it is better to ask what are my GH and KH, and are they suitable for my aquarium? For many freshwater community tanks, a stable pH is far more important than a supposedly perfect pH. Minerals also have an important part to play in the growth of aquarium plants. Because plants need nutrients to grow, and many of those nutrients are minerals.
[00:04:38] Calcium will help with new growth and cell structure. Magnesium is part of chlorophyll, which plants use for photosynthesis. Potassium helps with overall plant function and growth, while iron and other trace elements are needed in small amounts for healthy colour and development. If your planted tank has very low minerals, plants may grow slowly. They may show pale leaves, they may develop holes, or fail to thrive. But plant problems can be tricky. A yellow leaf doesn't automatically mean one specific deficiency.
[00:05:04] Lighting, CO2, fertiliser, substrate, flora, and maintenance all matter too. The practical point is this. Plants need a complete growing environment, and minerals are one part of that foundation. In low-tech plant aquariums, stable minerals, moderate lighting, regular fertiliser, and consistent water changes can grow many plants very well. So let's talk about ORO water. Now ORO stands for reverse osmosis. ORO water has had most of its dissolved minerals removed.
[00:05:32] And this makes it useful when tap water is too hard, too alkaline, or inconsistent. But ORO water on its own is usually not suitable for most aquariums. It's just too empty. Fish, shrimp, snails, plants, and bacteria need more than pure water. So if you use ORO water, you usually need to remineralise it. A remineraliser adds minerals back into the water. Some products raise GH only. Others raise both GH and KH.
[00:05:59] Some are made for planted tanks, others for shrimp, and others for harder water fish. The important thing is to choose the right remineraliser for your setup. And remember this. When water evaporates, the minerals stay behind. So for evaporation top-ups, you usually replace only the missing water. For water changes, you replace water with properly prepared remineralised water. And that difference helps prevent minerals from building up over time. One common mistake is assuming that clear water means healthy water. It doesn't.
[00:06:28] Clear water can still have unstable GH, KH, or pH stability. Another mistake is trying to change pH without understanding the KH. If the buffering capacity is high, pH will resist change. But if it's very low, the pH may swing way too easily. A third mistake is using ORO water without adding any minerals back. As stated earlier, ORO water gives you control, but it also gives you responsibility. Another common mistake is adding too many products at once.
[00:06:56] The pH adjusters, buffers, mineral blocks, crushed coral, fertilisers, and water conditioners, all together, all at the same time. Now, when you do that, it becomes impossible to know what's actually changing the water. The safest approach is to test first, adjust slowly, and keep your routine consistent. Here's a simple action plan. First up, you test your tap water for GH and KH. Then you test your aquarium water. You compare the results. If your tap water and aquarium water are similar, your minerals are probably stable.
[00:07:25] If they're very different, something in the tank may be changing the water. Maybe rocks or substrate, maybe evaporation, additives, or a lack of water change. Next, research the fish and invertebrates that you keep. Do they prefer soft, moderate, or hard water? Then decide whether you actually need to change anything at all. And this really is important. Don't adjust minerals just because someone online has different numbers to you. If your fish are healthy, your tank is stable, and your water is suitable for your livestock. Consistency may be better than chasing a perfect target.
[00:07:55] But if you do need to adjust your GH or KH, do it gradually. Prepare replacement water before adding into the tank. And avoid sudden swings. So let's do a quick recap here. Why are minerals needed? They're needed because minerals help to obtain water into proper freshwater habitat for your fish. They support fish health, balance growth, snail shells, shrimp molting, the beneficial bacteria, and the stability of your pH.
[00:08:20] GH tells us mainly about calcium and magnesium, while KH tells us about buffering and the stability of pH. Together, they help explain why your aquarium water behaves the way it does. And remember, the goal is not to chase perfect numbers. The goal is stable, suitable water for the animals and plants that you keep. So, after listening to this episode, go to your aquarium, test your GH to your KH, write the numbers down, learn what your tap water is like.
[00:08:46] That one step alone can make you feel like a much more confident aquarist. Now, I would love to hear from you in the comments. Have you ever had a problem in your aquarium that turned out to be linked to minerals, hardness, or pH stability? Share your experience. Let's learn from each other. If you're watching on YouTube, thanks for being on the channel. Please subscribe to the channel, like the video, and add your comments and share your experiences in the comments below. If you're listening to this episode on a podcast app, thank you for finding us and for listening to this episode.
[00:09:16] I do encourage you to follow the podcast and go ahead and leave a review. Leave a comment if you're able to on your app. That always helps us to grow the podcast and to learn from one another. But folks, once again, a big thank you from me for being part of the Aquarist Edge community. I look forward to sharing another topic with you in a week's time. Until then, keep learning, keep discovering, and keep enjoying this amazing hobby. Bye for now. That's it for this episode of the Aquarist Edge.
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