I set up a 35 litre coldwater tank on Monday ready for putting new fish in on Wednesday - as per advice from my local garden centre. I now realise that they didn't know what they were talking about and am worried about the health of the 5 fish they advised was a suitable number for this size of tank bearing in mind that the filter in the tank is a brand new one! The fish are 2 sarasa comets, two fantails and 1 black comet. I am also concerned that the filter is too powerful as it is suitable for upto 80 - 100 litres - again the advice of the "fish expert".
The water in the tank went smelly and cloudy overnight on Wednesday and so i decided not to feed them until Saturday to see if this helped, the water looked clearer today so i have fed them which they were very grateful for but i'm not sure what is the right thing to do - please help.

Hello GLEDWIN and welcome to fishkeeping Sorry to hear you were given the wrong advice, unfortunately we hear it all too often I could suggest that you take some of the fish back to the garden centre and tell them you were ill advised or you could weather the storm and see how you go on, I take it they are goldfish and only tiny at present, so should be ok for a while although you will need a larger tank as they grow, the main thing is the tank cycle, not nice on the fish but with regular maintenance, Part water changes, feeding a small amount once a day, testing the water parimiters "Ammonia, nitrite,nitrate etc" and generally keeping a close eye on things hopefully should help save the day The filter is the least of your problems right now and should be fine as long as the outflow is not too powerful for the fish.
I advise all our new members to read the other posts on here as you will find lots of information already written that should help you along, Good luck