befuzzled by water return options in aquaponics

I am designing my aquaponics system as I go because I was paralyzed by thinking through options. So I have taken up the shovel.

I've dug out a ~2000 gallon tank at the highest point of my yard. (the lowest point was already taken by tree roots and such.) Then I have two growbeds at 30 x 4 feet and 40 x 4 feet, on a slope with a three foot differential between the tank and the growbed endpoint. So that's where the water comes out... how to get it back up?

As you can see in the attachment, a mains-powered water pump is the default option. I would like to sustainably power the system.

Could I put a microhydro generator near the bottom, parallel to the growbeds, that recharges a battery bank and powers the return pump? Could I mount stationary solar panels that do the same? Should I just buy a normal pump, forget about alternative energy, and move on? I'd be grateful for your thoughts.

Rob Lisa wrote:Should I just buy a normal pump, forget about alternative energy, and move on?

Yes. I don't think the micro-hyrdo will work due to efficiency loss. Is this to be timed or constant flood?

Just make sure to put an anti-siphon thingie (I forget what it's called and husband/plumber is sleeping) coming off the FT. The nightmare scenerio would be for your sump pump to fail and all the water to siphon out of your FT.

I think there is something else wrong with your picture but it hasn't clicked for me yet...

Ah, your grow bed should not be sloped but level because water always is level. The way it is now your bottom plants will be flooded.

One more thing, your set-up is known as CHIFT/PIST (constant height in fish tank/pump in sump tank).
Googling that will give you more ideas:
https://www.google.com/search?q=CHIFT%2FPIST&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb

Cj, thanks a bunch for the replies. Lots of good info to think about.

I am planning constant flood, or at least I should say the water will circulate 24/7 with no timers. I'm aware of bell siphons but I'd rather do constant flood to reduce the temperature fluctuations that come with flood/drain cycles.

Level growbeds... that is something I have pondered as well, but decided it was better not to. In my thinking, water seeks its own level. So with a small input relative to the growbed volume, the water should flow down through the bed and exit at the sump, never really rising in the growbed. That was my line of thinking. It could be dead wrong.

The diagram may not be good enough but I don't think the tank will ever empty. I'm putting the pipe at the top. Worst case if the pump dies is I lose 6" of water from the top of the tank and the growbeds start to dry out.

I think you're right that this is CHIFT/PIST. I had kinda forgotten about it but now I will follow your link and read up on it again.

Thanks for taking a look!

Rob Lisa wrote:
The diagram may not be good enough but I don't think the tank will ever empty. I'm putting the pipe at the top. Worst case if the pump dies is I lose 6" of water from the top of the tank and the growbeds start to dry out.

No, you need the anti-siphon thing. You can try it without it and then turn off the pump. If the overflow pipe is full it will like continue to suck water out of the FT. If it's just a trickle than the water wont siphon.

It happened to me but it may have been a slightly different config.

Sorry, I take it back, sort of.

It can't happen with that set up but the set up is sort of wrong. You're supposed have a SLO (solid lifting overflow) to suck the solids off the bottom. The way you have it doesn't move enough of the gunk off the bottom of the FT.

How's it coming along? I am planning to do a 'trickle' system under gravel (lava rock).

It is a system being built in Costa Rica and the problem there is high water temp and low dissolved oxygen so raft systems do not perform well.

I like the tip on avoiding the temp fluctuation from flood/draining.

We are taking the best results from local operations and trying to make a system that will avoid the errors made before us! ...I thought maybe the trickle system under rock would work for your chift/pist design also...