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Buying Saltwater Tropical Fish

Fish Care

Red Fire Goby, Nemateleotris magnifica

Check out our new posting by Matt Leighton from on How to Choose the Right Saltwater Fish for Your Aquarium, which also includes information about how to introduce new saltwater fish to your aquarium. Thanks, Matt!

When you buy fish at a pet store, take the time to examine them careful.  Items to look for are:

  • No signs of disease on scales, fins or eyes for any fish present in the tank.

  • Good color.

  • Active swimming with no signs of struggle or gulping at the surface.

  • Not being beaten up by other fish in the tank.

  • Eating well.

Ask about compatibility with other fish you have.  Consider asking the pet store to keep the fish for you a few days or ensure they have a suitable guarantee.  Make sure you resist the temptation to fill a new tank with lots of fish, as the tank will not have cycled properly and you can end up losing most of your fish.  If you are a beginner, a couple of clownfish or damselfish are good starters.

When you buy online, you will need to do your research on the fish you are buying and then put your faith in the reputation of your supplier.  Consider quarantining new fish before adding adding them to an established tank.  Many fish are stressed by transport to a pet store or from online delivery to your door, because they are packed in the dark with pure oxygen and no way to naturally remove waste.  Fish can develop disease quickly thereafter.  Isolating them in a separate tank may soon provide evidence of disease that can be prevented from reaching your other fish.

It is always a good idea to float your new fish from a pet store in their bag on the surface of their new home.  This allows the temperature to adjust.  It is also recommended that tank water be added in small quantities to the bag in order to help the fish adjust to the new water quality.  Amquel can be added to neutralize ammonia.  Then discard some of the bag water and use a cup, a turkey baster or drip line to add small quantities of tank water.  Water replacement should be repeated several times until the new fish are effectively in the same water as that in the tank.  The fish can then be poured into the tank.  For a reef tank, netting the fish instead will help ensure that contaminates in the remaining bag water are not introduced to the tank.  Be sure to consider the type of fish though, as angels, tangs and lionfish easily tangle in nets and should be poured out instead.

Sending new fish to a quarantine tank first and dipping in chemical baths that kill parasites will reduce the risk of losing an entire well-established tank to disease.  A small tank with a simple sponge filter will suffice.  Use some rock or sand from the main tank to ensure proper biological filtration is established.  You should repeat the above transfer process when moving fish from a quarantine tank to the main tank.  This should be done after a week or two in quarantine.

If the fish have been delivered in the mail, follow the supplier instructions.  Online deliveries will have pure oxygen added to the bag and wastes will have built up, so opening the bag usually causes chemical changes and should only be done when the fish are removed from the bag immediately.

Adding new fish to an existing aquarium is not only a challenge due to the possible introduction of disease.  Fish in the tank have well established territories that they will vigorously defend and the new fish is at a serious disadvantage.