Ok. I understand better with the pictures. I didn't realize the smaller tank was a sump. I thought both tanks were on the same level and you were running water from both tanks into the inlet of the canister. Essentially a closed system with two tanks in parallel. What you have is an open system with two tanks in series. The canister is functioning as your return pump. The only thing you have to be careful of is maintaining the water level in the lower tank. If it gets too low and the siphon sucks air it will lose prime and not restart possibly causing the canister pump to overheat and lock up. An alternative is to place a submersible pump inside the smaller tank connnected to the inlet of the canister and remove the impeller from the canister and don't plug it in. This way you don't have to worry about losing prime.
Andy
