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my water tests are perfect but my fish keep dying!

When people learn that I’m an aquarist, I often get asked this question: My water tests are perfect but my fish keep dying! What’s wrong? The reason they ask me this is because it’s the most common problem experienced by aquarium owners, and they hope I have the answer.

While it can be heartbreaking to lose fish, there are several reasons why your test results could be perfect and your fish could still be dying. In this article, I will explain some of these reasons and what you can do about them.

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Top 3 Mistakes Newbies Make Setting Up Their Fish Tank.

Fish Aquarium With VallisneriaFish Aquarium With Vallisneria
Damitr, CC BY-SA 4.0, via Wikimedia Commons

Invest in a Good Quality Test Kit

In addition to your water tests, if you're having trouble keeping fish alive, consider investing in a good quality test kit.

The better your test kit, the more accurate of an idea you'll have on what's happening in your tank. Even though a high-quality test kit is going to cost you a little bit of money upfront, they'll pay for themselves over time with improved health and higher survival rates.

And there's nothing worse than spending hundreds of dollars on fish only to watch them die. Make sure your equipment is working properly and that it’s helping you make informed decisions before spending hard-earned money on anything else --especially new fish!

Know The signs Of Stress in your fish

Keeping an eye on your fish’s health is extremely important, especially when keeping them in a new environment. It's especially important that you monitor water quality since your fish's lungs don't exchange carbon dioxide and oxygen as efficiently as ours do, so ammonia levels can quickly rise if there isn't enough fresh water in their own tank. When toxic ammonia levels accumulate, it causes stress for your fish. 

So be sure to check the water quality at least three times a week, and change if necessary to have optimum clean sparkling water.

Check PH levels Regularly

PH levels must be balanced for fish to thrive. If you notice your fish start to die in large numbers, it could be a sign that your water’s pH levels are too high or low.

Check with your local pet store which can monitor and regulate your tank’s PH levels accordingly.

You can also add natural acidifiers such as peat or charcoal to help balance things out if you’re seeing problems with overall pH levels in your tank.

treat Sickness Before It Starts

To prevent fish from getting sick in the first place, you should be taking your water tests regularly and treating any issues that come up before they become an epidemic.

Some aquarists even set up a schedule for water testing: Every other day, once a week, once a month... Whatever schedule you choose, it’s important to follow it.

When things do get off track and illness sets in, there’s no guarantee that frequent water changes alone will save your fish. That’s why it’s best to take pre-emptive measures by treating sickness before it even starts.

Tropical Fish TankTropical Fish Tank
Neale Monks at the English-language Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

Know What Live Plants need

The health of your aquarium’s fish is dependent on three factors: clean water, good food and stable water chemistry.

Too often, aquarists focus on testing for ammonia and nitrites, not nitrates. However an excess of nutrients in aquarium water can lead to high nitrate levels which can be toxic to fish.

Nitrates begin to accumulate when you overfeed your tank or if live plants aren’t available to consume them. If you’re having trouble keeping your fish alive despite perfect water test results, check your plants; they may need additional nutrients or a change in their environment (i.e., lower light).

A Little Maintenance Goes A Long Way !

If you’re doing regular water tests and replacing your water regularly, there’s really no need to go any further. Some hobbyists have it in their heads that fish can only live in perfect water, but that’s just not true.

Most fish do great with routine water changes—so long as you follow a regular maintenance schedule. Ideally, aquarium owners should check their pH once a week and perform 10% water changes weekly.

If you don’t have time for that kind of commitment, simply do 25% (or larger) weekly or bi-weekly water changes instead. More frequent small changes can have a negative impact on overall fish health because it takes time for beneficial bacteria to catch up to new conditions.

Buy A Decent Filter (And Change It Regularly)

Most aquarium owners know that keeping fish is about more than just buying them—it's also about providing them with a home, equipment and habitat that meet their needs.

In other words, it’s not just what you put in your tank; it’s also what you leave out.

If there’s one thing many people overlook when setting up their aquarium, it’s a good filter (and regularly changing it).

Sure, you can get away with using your current filter for a while — but if you really want to ensure your fish have clean water to swim in and enough oxygen in which to live, make sure they don't get sick or die prematurely, change the filters regularly.

Do Not Overstock Your Fish Tank

If you’re an aquarium owner, you know how easy it is to get carried away. After all, who doesn’t want a well-stocked tank full of beautiful fish?

But remember that your tank needs time to develop and mature — and it takes time for each new fish you introduce to become acclimated. If you overstock your tank with too many fish at once, there won’t be enough room for them to swim comfortably.


It’s not uncommon for home aquarists to experience some fish mortality in their aquariums.

In fact, it’s a rare aquarium where there isn’t at least one or two dead fish at any given time.

However, if you follow our troubleshooting tips, we can get your tank back on track and keep your fish happy and healthy!

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