How To Tell If Fish Are Happy And Healthy In New Tank? (2021 FAQ Part 5)


How can I tell if my fish are healthy?

It is important to be able to tell if a fish is healthy or not, firstly so that you can choose healthy fish to begin with, and secondly, so that you can detect problems in your aquarium before they become too severe. If your fish are showing signs of stress or ill-health, it may be as the result of a disease or poor water quality. If left untreated, the fish may die. Most diseases, if caught early, are easily treated. Water quality problems can usually be solved by a prompt water change. What to look for: A healthy fish should be able to swim with little effort, stop and hold its position in the water. It should have a well-filled out body (the exact shape of which will vary with the species) and good colour. Fish will often not show their full colour in a shop situation as they are often constantly disturbed by observers and by other fish being caught in the tank. A healthy fish will hold its fins erect, be alert and eager to feed. An unhealthy fish may sulk in a corner, hang at the surface or sit at the bottom of an aquarium. However, these behaviours may be normal in some species, so it is important to know the usual behaviour of the fish you are interested in. Signs of disease to look out for include small white spots on the fins (particularly the tail), frayed or bloodied fins, cotton wool like growths, ulcers or other wounds, bloating of the fishes belly, or emaciation. Fish which are generally unhappy may also have their fins clamped against their sides. Frantic dashing behaviour in normally sedate species may indicate problems with water quality, as does fish gasping and hanging at the surface. If you think your fish may be diseased or that there is a problem with your water, see our disease guide.

What do I do if my fish die or get sick?

The first thing to do is to try to determine the cause of the problem. If a fish has died or looks sick, carefully examine all fish for signs of disease, and see our disease guide for help in diagnosing the problem. If a fish dies suddenly with no illness apparent, suspect your water quality. Test this if possible, or, if not, perform a water change. If your local store offers water testing, put aside a sample before changing the water and get it tested as soon as possible. If a large number of fish die very quickly, it may be that they have been poisoned. This can happen in extreme cases of over-feeding, or if some other toxin (detergent, fly spray etc) has entered the tank. Sometimes the only treatment is to move the fish into completely clean water. Although stressful, this is preferable to continued exposure to the toxin. You may need to strip down the tank and clean every thing very thoroughly with cold running water. If you are careful with your aquarium you should never have this problem. If a few fish die daily or over the period of a few days, suspect a disease and carefully examine all other fish for any signs or symptoms. If your fish appear just a little off colour but you can find no specific sign of disease, test your water, perform a water change, and add a dose or half dose of antiseptic or broad spectrum medication. It may be that water quality was declining, or that a disease was present and had not quite taken hold. Prompt action will usually avert any further problems. If water testing shows that water quality had declined it may be a good idea to do a second water change a few days later to get things back on track. If you diagnose a disease, treat it as promptly as possible, and make sure your water quality is spot on as you do so. Most common diseases are easily treated if caught early enough. If you are having problems diagnosing a disease, ask the staff at the shop where you buy your fish if they can help. If you take the fish in, they may be able to examine it and find the problem.

What happens if I go on holiday?

Unlike other pets, fish can safely be left unattended for short periods. If your fish are usually well fed, they will go for quite a few days without food. However, since fish are constantly looking for food, you do run the risk that larger or more aggressive species in your tank may eat or try to eat smaller species in the absence of regular feeding. Also, even species that generally do not eat plants will nibble on vegetation if they are hungry. If you trust a friend or relative to come into your house and feed your fish, this is a good solution. If they have no experience with fish, it is probably best to measure the food into portions for each feeding to be sure they do not give too much. If no-one is available to feed your fish, the next best option is an automated feeder. These can also be handy if you work long or odd hours and want to feed your fish at regular times. With automated feeders, you place the food for each feeding in a separate compartment, and they are released into the aquarium at set periods. Most can be programmed to feed at the time of day you choose, and to feed once or twice a day. It is best to slightly underfeed your fish while you are away to be on the safe side. If you cannot afford an automated feeder, or you go away only very occasionally, slow-release food blocks are available. These slowly dissolve and release food particles into the water. The rate of dissolution depends on water chemistry. Put in the minimum amount that will keep your fish from going hungry as excess food will pollute the water. In any case, it is a good idea to put some fine leaved plants in the aquarium. The fish can also nibble at these if they are hungry. Before you go, perform a water change and make sure your filtration and heating are working. Put your aquarium light on a timer or leave it off if you have no live plants. If you are leaving your aquarium for more than two weeks, it is best to get someone to check on the tank in your absence and to do a water change and replace food blocks if necessary.

How do I control algae?

The two factors which promote the growth of algae are light and nutrients. By controlling these factors, the growth of algae can often be minimised, without any further action necessary. Avoid placing the aquarium where it will receive too much sunlight, use only proper aquarium tubes to light the aquarium, and do not leave the lights on longer than necessary. If you are growing live plants, these usually need no more than 12 – 14 hours of light a day (and often even less). If you do not have live plants, put the aquarium lights on for just a few hours each day. Nutrients are removed by regular water changes, and by the growth of live plants. Even if you have live plants, it is still important to perform regular water changes, otherwise the balance of nutrients may tip in favour of the algae. Algae eating fish are an invaluable aid in controlling algae, and snails are also useful. If you have a persistent or fast growing strain of algae that you find you cannot control by these methods, you can use an aquarium algicide. Where plants are present liquid algicides are recommended as these are less likely to damage plants unless overdosed. In unplanted aquariums, algae blocks can be used and are even more effective, but they can damage live plants. Clean the aquarium and then use the algicide to prevent the growth of new algae. Note that, if you treat a heavily infested aquarium with algicide, it will do its job of killing the algae, but then the dead algae will still be rotting away in the aquarium, causing pollution and releasing nutrients for more algae to grow on. A few types of algae are resistant to algicides, eg black or beard algae.Β This usally must be physically removed and then an algicide can be used to prevent its return.Β Black algae often occurs where phosphate levels are high or where improper lighting is used, so check for these and remedy if needed.

How do I control snails?

Some snails are desirable in the aquarium, they help to clean up uneaten food and many also graze on algae. However, some species of snails will breed up into huge numbers if conditions in the aquarium suit them. This often happens where there is an excess of food in the aquarium, providing the snails with an ample supply. Snails can be controlled in a number of ways:

  1. Chemical methods. These treatments are often not effective and are not recommended. The active ingredient in anti-snail treatments is usually copper, which is removed by filtration. If not removed, it can be harmful to your fish and plants. Also, if effective, it is not desirable to have hundreds of dead snails in the aquarium as these will rot and pollute the tank.
  2. Removal by hand. Large numbers of snails are easily removed by hand. About half an hour after you turn off the aquarium lights, put a saucer, small dish, or net on the base of the aquarium and place either some sinking pellets or a weekend food block in it. The snails will soon cover the food and can be scooped out. Although you will never catch all the snails this way, you can reduce their numbers quite significantly. In addition, make sure you do not overfeed your fish, and the snails should remain under control.
  3. Snail-eating fish. There are a number of fish that eat snails and can be used to reduce their numbers. By far the most effective are clown loaches. Gouramis will also eat snails, but are not quite as eager, especially if they are receiving plenty of other food. Limit the amount of food your chosen snail-eating fish receive. Again, this method will not completely eradicate snails but will limit their numbers. You can use method 2) as well as adding snail-eaters in order to reduce snail numbers most rapidly
  4. Tank strip-down. This is another method that is undesirable, but it is the only sure way to eliminate snails completely. To kill snails in the gravel, soak it in very salty water then leave it out to dry. Scrub the sides of the aquarium and ornaments with a slurry of salt and water, and let dry. Do the same with your filter media, or replace it completely. When you put the tank back together, you must start from scratch again. Remember, there is really no need to completely eliminate snails. Limiting their numbers using either method 2) or 3), combined with improved tank maintenance, is the best option.

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