ahhh!

The flow should be reduced and if possible use a ball valve.

This may help you out.

 

anybody know it there is a flow controll on the pump?

 

+1
this is a remarkably simple and effective solution, plus its free!

 

Actually, you need to drill a hole in your return nozzel just below the water line in the DT, not above the waterline. Otherwise you'll get a jet Shooting water across your DT. The water in the DT will siphon out, but stop when it hits the drilled hole

 

No. Actually drilled holes and check valves are a false sense of security andcan and do fail even with maintenance. All it takes is a piece of algea, food, an anemone, a small fish or any number of things to defeat a drilled hole and a single grain of sand will defeat a check valve, remember it does not have to be a catastrophic failure, even a trickle will eventually flood given time like a power outage. You could clean either either one 10 minutes ago but that does not prevent any of the above happening and they do.

The only foolproof solution is a simple air gap, its the best method of backflow prevention, cannot fail and requires zero maintenance.
Its simple, just install your return so its slightly below the surface, this way when the pump shuts off only a very small,easily calculated amout of water flows back until the return is exposed to atmosphere and the suction breaks. Nothing beats an air gap. In my case I have a 100G display with a 30G sump. My returns are 3/4" below the waters surface so 3.5 gallons maximum (60"L x 18"Wx .75" deep /231= 3.5 gallons) can flow back to my sump in a power outage. I always keep about 8 gallons of freeboard or spare room at all times so a flood is not possible.

As long as you never overfill the sump you can sleep soundly at night.