I have recently purchased 3 angel fish and two neons for my 40 litre tank as advised by my local aquatic retailer. But one of the angel fish is very aggresive , he attacks the two angel fish and has killed the two neons!!!!!This is all within the space of two days ....I am a beginner and do not know what to do! Should I go back to the retailer and ask him to swap the angel fish for something a bit smaller and more manageable>?
Regards Claire

in all honesty yes you should take the angel fish back, and get a full refund.. and if there are any other shops around, leave and go there. they should not have recommended two angelfish and two neons for a 40 litre tank, that is a very poor recommendation! angelfish will quite happily eat neons, they do in the wild, so in a tank neons do not have much of a chance! two angelfish will also outgrow a 40 litre tank they can get to the size of a small plate, so i would avoid those with your tank, and neons should not be kept in two's either, minimum of 6, but 10 is better. small shoaling fish are ideal fish for a tank your size, if you have it planted too, it can look very impressive with a shoal of pretty fish, and some corydoras catfish would be nice on the bottom, they like to be in small groups too.
its such a shame when you get such rubbish advice from a shop. but it does happen, sadly we cant assume that because someone works in a fish shop that they know anything about fish... the best thing you can do is research yourself, and go into a shop already knowing which fish you want, then you can avoid asking any dummy assistants for whatever limited knowledge they have! of course there are some very good shops with staff that do know what there on about.. but finding them in a challenge.

Neon tetra's are an angelfishes natural food so they should not be in the same tank together. In some cases small angels and neons do co-habit successfully and particuly passive angels that are kept well fed often cant be bothered to eat the neons but its still a bad idea. Sadly many store still suggest them as tankmates - probably on the basis that neons are cheap and therefore expendable.

As you have discovered each fish is an individual with its own temperament and personality.

In the first instance return the agressive angelfish.

As Corraline has already said, 40L tank is too small for angels.

Thanks for your advice Coralline and Eagle C....will take them back tomorrow. What sort of sort small fish would you recommend for my small tank and how many? Dont want to ask reyailers advice again!!! Thanks!
Claire

How about a nice shoal of neon tetras? Poetic justice, IMO

Thanks Tetralinz...how big should the shoal be?
Claire

For a tank that size, really, I would recommend only a small shoal of 6.

Thanks.... the more information I'm armed with the better ,when I go back to the shop tomorrow!
Claire

...before you do, is the tank fully cycled? Do you have a test kit?

The tank previously housed two Oscars who belonged to my daughters boyfriend. They went to a new home with a bigger tank last week, they were in the tank for about 2 months . I did a partial water change yesterday (about 20%) butn opther than that the water is the same. No I havnt got a testing kit, should I get one and test before swopping the Angel fish for the Tetras.