The question "what can I put in my fish tank?" Presents itself to newcomers the first time they buy and set up their first aquarium, freshwater or marine who is. But back to appear even for those who already had experience with tropical fish, because they happen to set up a second tank, or simply because you want to add the fish seen in the store or a friend's house.
Unfortunately, we often give the wrong answer, thinking they can buy and raise a fish that actually has very different needs from those we know to offer him in our aquarium.
The ideal would be BEFORE then think about what fish like, and particularly interested in, read up on their needs and the maximum size that can be achieved, set up the aquarium to respect them as much as possible and THEN buy the fish in question.
Also because no one can trust completely to the retailer for our purchases, unless this is not really an avid aquarist And then a trader ...
ESPECIALLY Beware of pet stores that sell fish ALSO ... are the worst, the exceptions are very rare ...

If we know that we will have more than one species of aquarium fish, then it is also important to assess the compatibility 'between species: fish vs. fishes calm aggressive / territorial fish that live in hard water vs soft water fish that live in (values hardness), fish that frequent the same "water areas" vs. fish that are so different ... that the children could end up in the mouths of the greatest!

Some examples

1. the Gyrinocheilus alghivoro ... seems like a nice mouth has the "sucker", but actually eats very little algae in your aquarium and get to grow up to 25 cm ...
2. The classic fish dark, brown or gray, "clean glass" that you see in tropical freshwater aquariums are Ancistrus. They are also among the first fish to be recommended by the shopkeepers as " cleaners "for the aquarium.
   Avoid buying instead of their "cousins" because they grow very Hypostomus plecostomus, reaching as high as 50 cm!
3. Clown loaches (also called "clown loach") is a very beautiful fish and tough, but thrive in small flocks of 4-5 individuals can live up to 35 cm in length. Thus in general it is suitable ONLY for aquariums from 200 liters up, 300 to raise it in better group. Sold by retailers as a "natural remedy" to limit the number of snails in the aquarium ...
4. The sharks, both Pangasius (not shown in the absolute) is the Balantiocheilos, are fish that get very large over time, the former can easily exceed one meter in length the Balantiocheilos come "only" 35 cm ... which are many for Most of the aquariums on the market!
   Not to mention that they are both very lively, always on the move and can annoy other tenants.
5. Puffers (Tetraodon) are so cute ... but so hungry and aggressive, also want to brackish water. The only way to take some good has set up a brackish water tank with medium to large (120 liters or more).

Although it seems superfluous to remember that

• tropical freshwater fish, with very rare species, they need an aquarium with a heater for living well during the winter months, even if the aquarium is home and not outdoors.
• Clown fish live in salt water ... the sea ... you may not put them together with your goldfish, even if they look alike as color!