For anyone to give you any kind of diagram, need more info.
If you are going to use what I'm guessing
you want to use for a temperature controller I see the limitation being the output is 5a AC 110 (or possibly 220) The SSR's I use are switched via a DC switching signal. But seeing as the aquarium controllers are most likely ON/OFF controllers a mechanical relay is what you would want. And I see no problem since a lot of times I run my PID in ON/OFF mode. Not as exact, but if you know your controls you can accomplish the same thing.
Auber Instruments has inexpensive mechanical relay's
Do you have the specs for your temperature controller? or link to the actual one you want to use?