1. Never do a 100% waterchange! You will eliminate all the beneficial bacteria that have built up in your aquarium over time and are essential to breaking down any waste your fish produce.

  2. Never overfeed your fish! Feeding your fish too much, makes them produce too much waste, which deteriorates the water quality of the aquarium. Most fish will come up to the surface when they see you, even if they're not hungry, so resist temptation.

  3. Never put anything into your tank water that can harm your fish! Spraying toxic chemicals near an open fish tank or putting things such as hands or sponges which have had chemicals on them will most likely kill your fish. This also applies to any sand or natural decorations you find and want to put into your fish tank – they may have chemical residue on them and putting them in your tank can kill your fish.

  4. Never overpopulate your tank! Every tank has a certain amount of fish it can support and exceeding this limit leads to fighting, illnesses and bad water quality.

  5. Never introduce new fish without knowing whether their temperament matches the fish you already have! Tank mates need to be compatible because more aggressive or quick fish can harass other fish until they get sick or die.

  6. Never introduce fish which are much smaller than the other fish in your tank! If a fish is small enough to fit into another's mouth, chances are it will get eaten.

  7. Never leave it too long before you do a partial waterchange! The health of your fish will be in danger. Can you imagine what swimming around in your waste would do to you?

  8. Never forget to add water ager! Any new tapwater you put into your tank must have water ager added to it in order to eliminate the chlorine which harms your fish!

  9. Never change the conditions in your tank too drastically! Any sudden changes in water temperature, pH etc not only shock your fish, but if repetitive can lower the immune system of your fish to the point where it dies from stress. Do things gradually and your fish will not notice a thing!

  10. Never put a fish into the wrong kind of water! Saltwater fish into saltwater and freshwater fish into freshwater. It seems like a simple one, but it has unfortunately been done before. Ask your aquarium specialist if you don't know or do your homework.