Tropical Fish Questions and Answers

Author: Richard Guest of Pets Parade Team

How soon can I add fish to my new aquarium?
You should be able to introduce the first fish to your new aquarium 3 - 4 days after setting it up. You must ensure that the water has reached the correct temperature and this period is long enough for the water to heat up and to make any necessary adjustments to the heaterstat. Also ensure that the filter system is working correctly and add the appropriate amount of dechlorinator / water conditioner before adding any fish.

How many fish can I keep in my aquarium?
the exact number of fish you can keep will vary with the type and size of filter that you use, the frequency and amount of water changes and the size of the fish. However, as a rough rule of thumb 1" (2.5cm) length of fish per 12 sq in (30cm sq.) of surface area is a generally accepted average stocking rate (don't include the tail, just the body length of the fish). So a 24" long x 12" (61cm x 30cm) wide aquarium would support a population of 24 1"(2.5cm) long fish.

What is the correct temperature to keep tropical fish?
The majority of tropical fish are best maintained at a temperature between 77f° - 80f° (25c° - 27c° ) one notable exception is the Discus (Symphysodon aquafasciata) These fish fare better at a temperature of around 86f° (30c°).

How often should I do a water change on my tropical aquarium?
With an average community tank set-up 25% water change once a month is perfectly adequate. If you are keeping larger fish such as Oscars (Astronotus ocellatus) or discus, or you have a high stock density such as when keeping Malawi cichlids, then more frequent water changes should be made. Changing 20% of the water weekly may be more appropriate in these circumstances, if you are raising a brood of baby fish and feeding heavily you may even wish to change some water every day. It is important to use the right amount of dechlorinator with every water change you make and it is better to make several small water changes rather than one large one.

How often should I clean my aquarium filter?
Internal power filters generally need cleaning once a month, external power filters
may only need cleaning 2 or three times a year (when the water flow starts to slow). Remember that any sponge or other reusable filter material should be washed only in water that you have taken from the fish tank. Under gravel filters should be cleaned once a month by using a gravel cleaner/ syphon when carrying out the monthly water change. In heavily stocked aquariums or when large fish are being kept the frequency may need to be increased.

How often should I feed my tropical fish?
most small to medium size tropical fish do fine if fed 1 - 3 times per day, the golden rule is to feed only a small amount each time. Feed only the amount of food that your fish can eat in about ten minutes, any excess food can cause pollution of the aquarium water and may lead to fish deaths. With a new aquarium it is best to only feed the fish
once every two days for the first couple of weeks as this will limit the amount of waste the filter has to handle while it is still maturing.

My fish are dying and there seems to be no sign of a disease, what is the problem?
There can be many different reasons for fish deaths that appear to have no cause but probably the most common is poor water quality. Test the water for Ammonia and Nitrite,
these are both poisonous substances that enter the water from fish waste. Neither of these waste products can be seen, so using an aquarium test kit is the only way to make sure the water is safe for the fish. If levels are too high, reduce immediately with a series of 25% - 30% water changes and reduce the amount of food given, you may need to reduce stocking levels or install a larger filter to prevent the problem recurring.

How long should I leave the aquarium light switched on for?
10 - 12 hours a day is about right for the average tropical aquarium.

Why don't my aquarium plants grow?
First of all make sure you have genuine aquatic plants, many species sold for aquarium use are actually "marginal plants" and will never grow satisfactorily under water, it is best to purchase a good book with a chapter on plant selection to ensure the best type are purchased. Assuming that you have proper aquatic plants the next requirement is good lighting, a bright fluorescent tube such as a "triton" light should help and the use of a light enhancer/ reflector will improve matters even more. Regular additions of a good aquarium plant fertiliser will help and large specimen plants will benefit from a root tablet placed by their roots every few weeks.

The water in my fish tank is crystal clear, why do I need to test it?
Aquarium test kits measure levels of various substances in the water, the chemicals they test for such as Ammonia, Nitrite and Nitrate are dissolved in the water so can be present in large amounts even if the water appears perfectly "clean". It is important to develop a regular test routine and record the aquarium water conditions on at least a monthly basis, this will avoid many of the most common fishkeeping problems that arise from poor water
quality.

Is it ok to turn my filter off at night?
No, the filter system should be kept running 24 hours a day. The biological filters that most fish-keepers use require a constant supply of moving water to supply oxygen and "food" to the living bacterial cultures that break down the fishes waste products and maintain correct water conditions.

Will my fish be all right without food when I go on holiday?
You can add a holiday block to your fish tank before you go away, this will slowly dissolve over a 10 - 14 day period and ensure the fish have a steady supply of food. Well-fed and healthy fish will be ok without food for a 2-week period anyway, the choice is up to you.

Do I need to have an air pump making bubbles in my tank?
No, a filter return that creates a water flow at the surface will add oxygen to the aquarium by agitating the water surface.

What is the best type of filter for a tropical fish tank?
There are many types of filter and most types work effectively, in general an internal filter such as a "fluval" or an undergravel filter will be most peoples choice for a general community tank set-up.external power filters are popular for aquariums containing large fish as they can better handle the large quantities of fish waste created.

Do I need to keep any water treatments for my aquarium?
You should always have a bottle of dechlorinator / water conditioner to remove chlorine when carrying out water changes. It is a good idea to keep a bottle of parasite treatment such as "protozin" for treating out breaks of Whitespot disease or other common parasite problems that may arise and a general antibacterial treatment for any cases of fin rot or other bacterial damage. When treating small fish speed is of the essence, so once the problem has been correctly identified it is better to have the right treatment to hand than to have to make a special trip or wait for delivery.

What is the best way to introduce new fish into my aquarium?
Turn off the aquarium light, float the fish on top of the water in the unopened bag they came in for 20 - 30 minutes to allow the temperature of the water in the bag to slowly adjust to the tank temperature. The fish should then be ok to let out. Leave the lights off for another hour or two and feed the other fish to allow the new fish to settle in while your existing stocks are distracted. This advice applies to most hardy tropical fish species, where your water chemistry is similar to that in the dealers' tanks. For more delicate species or when there is big difference in water chemistry it is better to slowly mix some of your water in with the fishes transport water over a period of an hour or more. Advice on the specific type of fish purchased should be sought from the dealer.

Do I need gravel on the bottom of my tank?
the short answer is no you don't need to cover the bottom of the fish tank with gravel (unless you are using an undergravel filter) but most people think some sort of covering looks better and the fish seem to prefer it. Alternatives to gravel can be used e.g. sand, but make sure they are non-toxic and won't affect the water chemistry. When growing on baby fish many people prefer to keep the aquarium bottom free of gravel as this makes it easier to remove waste when feeding several times a day and carrying out frequent water changes that are required when raising a large brood of hungry fish.

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