Water flow, can the pump be too big?

[Charlotte Seibert]

Hi all, I dabbled in aquaponics a bit a few years ago., even though I went against some of the rules (as in using 2 pumps and 2 timers) I did pretty well. Some things came up and I had to pull my system down, Well I am back at it and have some questions. I still have my grow media and 200gal fish pond. I am putting up 2 grow beds for a total of 24 sq ft of grow area. I will be pumping a height of 5 ft., flood and drain using an indexing valve. I have to get a larger pump, question is can your pump be too big? Can you cycle too much water. I found a fountain pump that pumps 1200 gph @ a 5 ft lift. Given that I will only be pumping 30 min out of each hour, that's 600gph or 3 times my tank. Some of the water being pumped out will be sent  back for aeration.  

[Johan Prins]

Hi Tuna,

Your set-up is almost like what I had:

I initially also had a "sorta" return line (my pump came with a double valve on a tee, allowing to divert some of the water right back into the sump at the exit of the pump).

Since I use a float switch anyway I later I opted for leaving the pump line fully open, take the diversion valve out, and I have a check valve in the line, so the fish tank can't be siphoned back to the sump.

This way, my pump runs about 50% of the time, as long as I don't add more grow beds, at least.