Hello there. Oh really? I did lots of research before choosing fish, and I read that the minimum tank size for Corys and Harlequins is 10 gallon.Welcome to the forum
I'm afraid the tank is too small for harlequins and cories, both of these species need a 20 gallon tank. Corydoras and harlequins need a shoal of 6 or more and soft water.
There is a lot of misinformation around. They both need a 20 gallon tank, harlequins best do in a 20 gallon tank and you also could put in more than 6 of each species.Hello there. Oh really? I did lots of research before choosing fish, and I read that the minimum tank size for Corys and Harlequins is 10 gallon.
I do agree with @Salty&Onion a 20 gallon would be better, they need the extra room, you do have a nice looking tank. I have a 20 gallon and really like the size and how easy it is to work in.Which doesn't mean they're happy in such small tank.
I'd recommend you getting a 20 gallon tank as it gives your fish space and more stocking options.