return pump not strong enough for drain ?

hey just posting this because i have a 190 gph pump returning to my 30 gal brackish green spotted puffer, but the drain which is a regular tube siphoning isnt siphoning enogh water, if i add another tube will this be too much drain for the 190 gallon pump, will it ever be too much or will the pump just keep pumping so the drain doesnt break the siphon

 

The overflow will balance out with the return pump, the pump will determine the water level in the display and how fast the overflow drains.
Remember your pump is probably 190 GPH at 0 feet of head, at 3 or 4 feet of head its probably just trickling out so the overflow only has to match that flow.