While you can use a 12V DC motor if you have a very good PSU, I don't recommend using an air pump for circulating liquid.
Yes but can i connect 12V motor which is meant for 15A on 30A 12V connector?
I totaly agree. Using air pump would be stupid. But never intended to do that. I just took the motor out of there. I have whole construction made other way. If you want i can show you pics when I'm done. Hope it will be soon.