Buying Fish - What to Consider
To ensure your tank is as healthy as possible, it's important to make the right choice of livestock. There are several things you can look for when assessing a fishes' health. Don't be afraid to speak to your supplier as well, and find out where their stock comes from. I hope you find these guidelines useful.
Choosing Healthy Fish:
If you see new arrivals in your fish store, it's often a good idea to find out how long the store has had them, and whether they've been in quarantine. Fish that have literally just arrived should be avoided as their stress levels are already high and they may die.
Many fish shops will (and should) tell you if the fish are new, and may suggest you wait a couple of weeks before purchasing them.
Looking for Illness & Damage:
Colouring - A healthy fish has rich, bright coloring, whereas a sick fish will probably have faded. Any pattern in the scales should be distinct, with no colours blurring.
Excretion - A sick fish may have trailing colorless excrement.
Swimming Ability - A sick fish may be listless, and may have difficulty staying afloat or maneuvering. This is often caused by swim-bladder disorder. A healthy fish swims steadily and with ease. Healthy fish can stay perfectly still in one position if they so choose.
Body Shape - Protruding scales (giving the fish a pine-cone effect) is a sign of dropsy
Damage - Fish with damaged scales, open wounds, lumps and bumps or split fins should not be purchased. They are already sick and could well affect your other livestock.
Fins - A fish with erect fins that swims happily is healthy and not stressed. A sure sign of a stressed fish is one with its fins closed into its body plus other symptoms. However. some marine species do naturally swim with their fins closed.
Behaviour - A fish that moves little or stays in a corner should be avoided. This is a sign the fish is unhappy and may be sick.
Considering Size:
Usually new fish are sold as juveniles, so it pays to know how big your chosen species will grow before making any purchases. Some fish can grow exceptionally large, and in an understocked tank may grow quicker than you anticipate.
Compatability of Species:
It's important to understand how your species behave in relation to others. Some fish are very territorial and may fight other fish, especially during breeding periods.
For example, male Siamese fighting fish (betta splendens) should be kept apart from other males, as they will fight to the death.. They are also known to attack smaller fish with similar tails, such as Mollies and Guppies.
Blue-Velvet Damselfish won't tolerate another of its species in the same aquarium. You should consider whether your fish needs others of its own kind, such as the Clown Loach, or swims in a school, eg. Chromis (marine), Tetra (Tropical).
Adding New Fish to your Aquarium:
When doing anything to an aquarium, remember that what seem to be small changes to us are actually huge changes for fish.
Everything must be done slowly and carefully, giving the fish time to adjust and keeping them stress-free. To equalize the temperature in your fishes' bag with the temperature in your aquarium, you should float the bag on the surface of the tank for 10-15 minutes to give the temperature time to settle.
During this 10-15 minute period, slowly add small handfuls of tank water to the bag to equalize any chemical differences the new fish may experience. If you feel any existing fish may pester the new arrivals, try putting a little bit of food in to distract them while you add the new fish.