Backyard Aquaponics
A place to discuss aquaponics

Or overflow into the next GB to save some power. May as well use the water once its been pushed up hill. If the GB's are on the flat any overflow could shunt to the next GB if you just plumb them all together at overflow level, then install a slightly higher placed overflow back to the sump once all GB's are full.

Bullewinkle, excellent idea.

Actually, on second thought, that might be really hard to implement.

Last night it seemed like a good idea, but this morning, not so much.

If you're controlling how much goes into each GB with a tap, it wouldn't do much except when something goes wrong. And when something goes wrong, overflowing back to the sump is the safest bet, otherwise you might just be cascading your problem to the next bed.

Are all the grow beds on the same level? Flat concrete or something?

The grow beds will be the same level. The greenhouse floor is flat concrete. Yes, I was originally planning a gravity fed supply to the growbeds, with flow rate controlled by a tap (ball valve). An elevated standpipe that overflows into the sump seems feasible.

Maybe I misunderstood what you were suggesting. Did you mean the growbeds should be "stairstepped" from higher to lower level so the supply can "cascade" from upper to lower level? So the the water supply does the same?
I like the idea, but think it would be more complex then I would care to pursue. I would like to keep it simple. I do appreciate your input. Sharing different ideas is what a a forum like this is all about.

Bullwinkle maybe what your suggesting would be synonymous with a "series" wiring schematic. Whereas I am thinking of "parallel." In regard to pumbing that is.

No, I was just thinking that any excess going to any given bed could overflow to the next, but I think that's harder to do than it was to say.

I agree, easy to say, hard to do.

I have a few suggestions if they aren't too late.

First on the growbed stands- keep the stands intact, use the growbed in the lower portion and use the higher part of the frame for tomato support. If you need the growbed to be higher for proper drainage to the sump, build it up with cinder blocks- it's cheap and strong. This will keep the center of gravity lower to the ground as mature tomato plants are heavy and will need some sort of support anyway, not only for ease of picking the fruit but for management of the plant itself. Of course, this is assuming that you don't intend to tie up your tomato plants in another way.

I don't think you mentioned your type of water pump- in-line or sump but either way, pump the clean water from your sump tank up to your fish tank and any overflow, re-pump back to the the sump area. That may sound redundant but your pump will last longer, if there isn't resistance against the flow output and it may be necessary if you find that your growbeds won't drain as quickly as they need to, in regards to pump output. There should also be less cleaning maintenance issues as the solid fish waste will all go through the growbeds and get trapped there and not through the pump first. Do make sure that the fish water is changing out sufficiently so the fish won't die from lack of O2. If that is an issue, you will have to add more grow beds to handle the water volume needed or drain the fish tank directly into the sump area, which is not ideal as that will make more maintenace issues to remove the solids as now your sump has now become a settlement tank as well.
Also if you create splashing to capture free O2 for the pond/raft portion of your system, you are not completely wasting the energy you're paying for. You can eliminate splashing directly onto plants using food grade plastic to cover the ends of the spouts and drape it into the water itself and/or use tees with an open end standpipe at the top for the air to get in. The water force through the pipe will drag air in as well, you just need to make sure the tee riser is high enough that water won't back up and leak out.

To keep the fish tank at a constant level, use an outside stand pipe and I would also recommend a fish tank overflow drain above this height so if the primary fish tank drain gets plugged for any reason, you can see that without having water all over the ground. Doing an external standpipe, you may not need to raise the fish tank at all or maybe reduce the height required. Lifting that much weight could make it unstable and unsafe as well as difficult for routine operations- inspection, feeding, cleaning, ect.
You only need to be higher than the next level to have drainage as water always seeks it's own level of equilibrium.

Hope that I was a help.