I am upgrading my tank soon. I have seen a 300L (79gallon tank) i want for my four fancy goldfish. It is 4ft long. 1ft and a half wide. But its 27.7 inches high. Is this ok cause i heard you shouldnt keep fancies in tall tanks. Is there a reason for this?. I will be putting my 3 danios and 4 clound minnows in with them when i get this tank. Is that ok stockwise too?.