Hi Colmanburns,
You have chosen quite big fish for a 40g and if the algae eater is a plec and not a Chinese algae eater then those 3 fish should not be sharing that tank.
In the past, before the invent of the Web and forums, I kept single large specimens in about 35-40g tanks. Their behaviour was all wrong and now I understand why. In the wild Fish territories are large and opportunity to swim is almost endless and in a small tank I believe they just go mad, or the fish equivalent.
I have a 60g with fish no bigger than 2" fully grown. They are well proportioned to the size of the tank and the behaviour is as near to wild as possible in the confines of a tank.
You might have to have a rethink on your present stocking if you want a successful tank.
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