i have used one of them calculations about the length of fish and the amount of room they need any evrything is fine, my tank may actually be more than this anyway cos i dnt know exactly how many gallons are in a litre or the other way around. I have read on websites about keeping certain fish together and my fish all get on fine, the male betta i have isnt very aggressive at all and doesnt bother any of the other fish- not even the females, My tank is heavily planted and the fish have many hiding places, and also i have a spere large tank to allow any fish that are not doing well in my main tank allthough this has never happened. I have actually had a local fish specialist round b4 and hes told me that im actaully very lucky with the fish ive got and im always very careful to introduce fish that may not get on. I puirchased myself a pair of angels yesterday and they get on fine, they have alot of room and seem very happy and healthy aswell as the other fish. If anyone knows how many litres are in a gallon i may be able to put the correct gallons of my tank. Thanks 4 tryin to help