Backyard Aquaponics
A place to discuss aquaponics

I was wondering about flow rates for the H2O filtering through the gravel beds. What do some of you guys/gals do? Continous flow??? Timed??? or do you fill the gravel medium and let it sit a while. Is there any research out there as to the nutrient uptake rate of the plants in either of the flow systems.

Thanks for all comments

Be blessed

Jason

Botswana, Africa

Most of us here do flood and drain (there is at least one successful exception who runs his beds continually flooded) Anyway, we flood and drain either using a timer on the pump to flood the grow beds to a point and then they slowly drain while the pump is off. Others run the pump continuously and use auto siphons or other such things to automatically drain the beds quickly once they flood to the desired level. Then there are some alternate methods of doing things (my pump runs constantly but the grow beds are flooded in sequence using some valves.)

The plants don't seem to mind much one way or the other so long as there is plenty of aeration in the water and the surface of the gravel doesn't get wet. The Flood and drain method ensures the plants get enough aeration. In continually flooded beds, one must ensure there is plenty of aeration of the water to keep plants from suffering root rot.

I don't think there would be much advantage to filling a bed and letting it sit before draining though some people allow water to continue flowing through a bed for a while after it has filled before the pump shuts off and that is fine so long as there is an overflow to keep the bed from flooding over the gravel.

I don't know if there have been any studies about what flow rates are best for nutrient up take. So far by experience among members here, it seems to not make a whole heck of a lot of difference one way or the other to the plants. The nutrient is in solution and all the surfaces in the grow beds that get wet, will stay wet for a period of time and the plants will use what they need from that film till the flood comes again.

Thanks TCLynx

If that is the case wouldn't a continous flow also provide more disolved O2 back into the fish tank provided there is enough height from plant bed to fish tank?

tks
Jason

Continuous pumping can provide extra aeration to the fish tank. Continuously flooded beds probably provide a trickle back tot he fish tank where the splashing in might provide some aeration but the water itself may be pretty depleted of oxygen before it goes back to the fish tank. A continuous pumping system can still have flood and drain grow beds though by autosiphons. I run continuous pumping in a CHIFT PIST system where the flow from the pump is constantly splashing into my fish tank. Water flows out of the fish tank to sequentially fill grow beds by use of some special valves. The water from the grow beds splashes back into an in ground sump tank where the excess flow from the pump is also going and the pump draws the clean aerated waterfrom the sump tank to spray back up into the fish tank. In addition to all that, I have an air pump and air stones for my system and there is a relay and battery backup for the air so if mains power goes out, the air pump will switch to battery power and keep the fish alive for at least a day.

So what you are saying is that i will need another source of O2 rather than just the a constant flow/splash back into the fish tank. If that is so how do you think a few of the floating solar power fountain pumps would work. If there is one thing that we have plenty of in Botswana it is sun. I'm sure I would have to rig something up for at night but I need to consume as little energy as possible. I will be out in the bush and will have to come up with my own power source for the whole farm and orphanage. It will be mostly biodiesel run generators and a large bank of batteries which will be charged by a diesel engine and several alternators.