Keep Your Fish Healthy

Author: Last updated:

Healthy aquarium fish

Just when you think you have everything under control with your tanks, something is bound to go wrong. A mystery illness, occasional losses, lethargic fish, dull colours or slow growth are all signs that something is missing and your fish are not in as good a shape as they could be. Providing your fish with correct water conditions, regular feeding, and a suitably sized home are essential conditions for survival, but to get your fish to really thrive, you have to go the extra mile.

Environmental enrichment

A typical aquarium is a glass box with water, gravel, lights and a few ornaments. You could compare this to a room with a carpet, a sofa, and a coffee table; you could live in it, but its not much fun. What your fish need is the human equivalent of a Playstation, home cinema system, and a large garden with a trampoline. Environmental enrichment is giving your fish an environment with plenty of areas to keep them occupied, much like they would be in nature. This does not mean fluorescent ornaments, air powered divers, and plastic 'mazes' to confuse and trap your fish, but a more natural approach to aqua-scaping. Densely planted areas, surface cover, caves, quiet spots, and areas of flow are all natural components of an enriched aquarium. Individual species may have different requirements, but the majority of small aquarium fish will benefit from planted areas, scavengers such as small catfish and loaches will appreciate caves and hiding spots, and midwater 'torpedo' shaped fish will benefit from flowing water. Including as many of these components as possible will result in more diverse behaviour making your fish more interesting, livelier, healthier, and happier.

A Healthy diet makes healthy fish

I've heard rumours it is possible to survive on Guinness and potatoes, and although I enjoy an occasional pint of the Irish stout, I wouldn't like to imagine what living off it might do to me. Quality branded foods provide all the essential ingredients your fish need to survive, but feeding a varied diet has plenty of other benefits. Treats, which are particularly enjoyable by many fish, can liven up your fish, and difficult to eat foods will make your fish work for their dinner, providing further environmental enrichment. For most fish, at least half of their diet should be made up from proprietary dried foods like flake, pellets, or crisps, which provide all the main staples and vitamins. Always use a known brand and avoid foods that are sold loose, since exposure to air, moisture, and light will all reduce a foods quality. To vary up your fishes diet try frozen foods or live foods and progress to occasional fresh foods. Grazers and algae eaters will enjoy most vegetables; slices of cucumber, courgette, shelled peas and lettuce are ideal. Most fish will nibble at fresh fruits and since we are all told to eat more fruit, I try and make a habit of eating soft fruits with stones or cores like mangos, plums, or pears and dropping the remains in my tanks for the fish to graze on for half an hour or so. Whilst a few other foods can be fed to fish, for safety it is best to stick to fresh fruits and vegetables.


With a good varied diet, your fish will remain active and healthy, although a side effect is that they can become fussy eaters and may turn their nose up at more boring foods. This can be helpful because it will help to stop your fish from eating more than they need, but it may also mean they do not eat the dried foods which are more nutritionally balanced. A good solution is to have a day each week when your fish get no food at all. A fast day will ensure your fish are eager to feed on whatever they get given the next day, and they will also hunt the aquarium for leftovers (although with correct feeding levels there should be no leftover food) Fast days are only suitable for well established and healthy fish, which will cope for several days without feeding, and if they get used to regular days without food they will be fine if you have the occasional weekend away.

Set your day length

Fish have a body clock that prompts them when to carry out certain actions such as spawning, hunting, and resting. For the most part, this is set by the daily cycle of light and dark. If your fish are subjected to varying artificial day lengths by the lights being turned on and off at different times each day, their body clocks will be confused and they may begin to act unnaturally, becoming lethargic, timid, or boisterous. Setting your lights on timers will give a set period of light and dark which is the same each day. Your fish will then know when it is 'lights on' and 'lights off' time, reducing the shock of a sudden change in light and allowing their bodies to 'plan' their day.

Polish your water

Even with good filtration, chemical pollutants can build up in an aquarium over time resulting in a deterioration of health and often causing 'mystery' deaths. To prevent this, use activated carbon and/or 'polishing' medias such as poly-filters several times a year to remove any build-ups in the water. Many filters have carbon in them, and these need replacing on a regular basis if they are a permanent part of the filtration.

Avoid excessive treatments and chemicals

Many fish keepers fall into the trap of adding unnecessary treatments to the aquarium based on the instructions of manufacturers wishing to sell more products. Whilst the multitudes of available treatments, additives, and remedies available all have their uses, in an average established aquarium the only essential treatment is a water conditioner or de-chlorinator to treat tap water. If you use anything else it should be for a specific reason and only for the time period needed for the problem to fix. Using chemical treatments as disease preventatives will put stress on your fish, and disease pathogens will become more resistant; using excessive fertilisers when plant problems may lie elsewhere will result in excess algae growth; using bacterial starters in mature tanks will result in fluctuations of waste pollutants.

Learn more

The best thing you can do to make sure your fish are as healthy as possible is to learn as much as you can about them. Whilst it is essential to find out the basics such as how big a fish gets, how peaceful it is, which fish it mixes with, and whether it has any unusual requirements before you purchase, it is equally useful to research your fish as much as possible once you have them in your tank. For instance, finding out about a fishes natural environment, what it feeds on, and how it lives can be invaluable to shape your aquarium to its needs. Researching will also uncover plenty of tips relating to specific fish, which might not come under the category of 'general care'. Finding out that clay pots make ideal caves for Kribensis, that many sucker-mouth catfish need bog-wood to graze on, or that some fish are over-sensitive to bright light are just examples of the items of knowledge you can gain by carrying out some proper research. Learning about your fish is part of the enjoyment of the hobby, and will allow you to appreciate your fish even more.

Click to read the Latest Tropical Fish discussions from Thinkfish users.

Think Fish Tropical Fish Forum
Tropical Fish Market Place
Fish of the month

Helping Fishkeepers With Their Fishkeeping Needs Since 2006