Question about pumps

So I've been running a pretty simple DWC style setup, it has a single 5 gallon bucket, an air pump + air stone, and a submersible pump + aquarium chiller. Overall I love the setup, it's simple but gets the job done... Mostly.

The biggest problem I keep running into... Is that submersible pump. In ~ 7 months I've replaced it twice. It pumps water through about 10 feet of tubing with no significant changes in elevation (The tubing drops to the ground... The bucket and aquarium chiller are also both on the ground)... And it just burnt out on me again.

But... I have a decent diaphragm pump. It's a 12V 10A pump I have hooked up to a speed controller that I normally just use for res changes. I'm really tired of fighting with these little pumps. Could I hook up my diaphragm pump and just turn it way down? Or would constantly running it so low burn out the motor? Or anyone have a recommendation for a reliable low-power pump I could use for this?