Backyard Aquaponics
A place to discuss aquaponics

Built my first system using the (2) 55 gallon barrel plan. (1 barrel cut in half and 1 used as the fish tank)
Everything works great. I bought a 600 gph pump on sale at HD and when I tested the system it will fill up the two beds in 5 minutes.
I have been reading Ms. Berstein's book and other articles and the common denominator is to run your system on for 15 minutes and then off for 45 minutes.
In that time period, 15 minutes, I will cycle the water going into the grow beds 3 times.

Will this cause an issue?

I have ball valves on the line but I’m not sure if I can reduce the water flow without damaging the pump.

Not knowing what kind of pump you've selected, I can only speak for mine... and it had an adjustment on the pump body. Since it is new, it is fab... no gunk yet, no fish waste, I only checked it at 3' head, and it is gang busters... I'll be running a barrel system, too. I only have three-- and I intend to get 'em all running, eventually, but I'll start with the first two to cycle... then add one a month, or when I can afford plumbing.

Mine is only a 300 gph. I'm running on a shoe string. It was what I could afford, for now.

Are you 'cycling yet', as in your media is in the half barrels? Your drain time may cut down once you have media to trickle through... not your fill time, just the drain time.

You still want to cycle one grow bed... then the other grow bed, I believe. Time with air on the roots is good, tho the media will still keep them damp.

Depends on the 'head' you need - in the simplest systems the water drains from the GB's straight back into the FT - that is a metre of head right there, so your 600gph is now (say) 500gph.

My preference for oversize pumps is to put in a T-piece connector and have a ball valve on the leg you run back to your FT. At the end of that leg, in the FT, attach a short bar with small holes drilled in it along a line so that you can turn them to face into the water below. Adjust the flow using the valve until you get your 15min to fill the GB's.

Hint: Don't glue your spray bar. It is handy being able to turn it to get best aeration and to add holes if needed. Also don't make the holes too big - you want a little bit of pressure behind the jets.