Backyard Aquaponics
A place to discuss aquaponics

I have been looking at the various systems shown here and have noticed how many use a sump to which the water drains before it is pumped back to the fish tank.

Why does one need a sump? Why not just keep the growbeds higher than the fish tank and let the water end where it began without having to pump a second time?

Does this have to do with the amount of water in the system? The height of the fish tanks?

Thanks.

CHIFTPIST My fish tanks are above my grow bed. They over flow into the growbeds. A sump where the water goes from the grow beds. Its a one pump system with not fluctuation in fish tank water level. Pumping from a grow bed might work, might not; either way you need a common point for pumping.

Also, in large systems where the water tank is large, it might not be practical to raise the grow beds above the fish tank. You would need a ladder to maintain your beds. So a sump is need to collect water returning from multiple beds.

If you dont mind the fish tanks water level going up and down all the time then yes its no problem to have just a grow bed that drains back to the fish tank. Just make sure you do not over stock the fish tank.

The usual reason is that for flood and drain when all beds are flooded the fish tank level goes too far down. The sump is a reservoir to account for this fluctuation. For beds of say twice the fish tank volume with 30% ratio of water to gravel then for a 100 gallon fish tank and 200 gallons of gravel beds your fish tank would go down to 100 - (200 * 0.3) = 40 gallons for the fish, which would suck. Add a (minimum, full) 50 gallon sump and the fish tank level won't go down at all.

Yep, two major reasons for a sump. Either gravity and layout don't make draining directly to fish tank reasonable so sump tank and extra pump needed or you don't want your water level to fluctuate in the fish tank so use the sump tank to absorb level fluctuations.

My reason for wanting a sump, if the water is filtered through grow beds before going into the sump, pump stays cleaner and requires less maintenance in a single pump in sump system. I'm having to clean out my pump trap twice a week lately and the fish are not even eating much since it is winter here.

+1 for cleaner pump. Will double the life and reduce maintenance.

Especially oce your system is heavily stocked with fish.

You can also use a sump to keep fingerlings in, or yabbies, or water plants that will be damaged by fish.

Every chance that a pump in the FT will lose it's grille at some point (has happened to me twice) and you'll get 'fish scale confetti' in your growbeds.

'fish scale confetti' - can't remember who coined that one

I have a flood and drain system without a sump. The growbed is built over the (dugg in) fish tank, and is much smaller in area and volume. This way, the water in the fish tank only goes up and down about 5cm. Problems I have with this setup is that the pump has to pump up solids, and gradually clogs up (I have to clean it at least once a month, depending on how much I feed). This also means that the water input into the growbed gradually gets lower, which makes it difficult to use an autosiphon reliably.

If I had read about the chift pist principle, I may have built my system differently. The idea of the pump only pumping filtered water seems great, and the added sump can be used in many ways. It is good to have a seperate tank to grow fingerlings or put crayfish in (or use as a quarantine), and the added water volume makes the nutrient solution and water temperature more constant. You could also put gravel or clay pebbles in the sump for extra biofiltration (means less water volume, though).

But if your fish tank is large enough in volume, you technically don't need a sump.

Another good reason for a sump is protecting the fish tank from accidental drainage. Should you spring a leak somewhere between the grow beds and fish tank, and not notice until it's too late, there's no chance of accidentally draining the fish tank.

I don't have a sump. But the FT volume is large enough not to worry the fish. And so far pumping solids has not required any cleaning. I sweep the bottom every now and then towards the pump.

But if the flood cycle takes too much water out of your FT a sump would help prevent stress on the fish. Also they make great places to grow duckweed. As it does not last in the FT for long.

This is what i was looking for! A sump under the grow beds with only one pump.
Does this mean thou that you need larger diameter pipes to go into the GBs so that the water coming out of the FT doesn't overflow the FT?
But also does this mean that FT has temps more inline with air temps?

If im understanding your question right i would answer yes. The pipe running into the GB should be larger than you may expect. It needs to carry all the water that you are pumping into the fish tank under only the pressure created by gravity. I use a 50mm outlet (as that was all the tank could take) and that just handles about 4000l/hour but if that one blocks up with even a few leaves the level will rise and exit through my top overflow and return to the sump.
Both my tanks have 2 outlets incase one blocks. Pump in sump is great and if you keep it dark it even stays clean and as OBO says pump should last a very long time without any grit going through it.

Adrian check out mizzie system it will explain a lot

My system is 10 gallons with a shoebox size growbed and I can even see the height change in the fish tank between start and finish of the single growbed draining, around an inch in height. If you plan to use this method, adjust your maximum fish stocking density to calculate only half of the fish tank's worth of water. Also be careful of "topping up" the water in the fish tank when there is water in the growbeds getting ready to drain, don't want to have it overflow the top of the fish tank.

thorn,
If you are pumping your water from your sump into the FT then the only rise would be if you don't have a big enough outlet to your GB. Once the pump stops so will the draining from the FT.
For the design i'm looking at doing is having a header tank after the FT. The HT is the same size as both the FT and sump just because i can thats all. So if i find that the GBs are getting too much water too quickly i can hold back the water pressure in the HT, without losing the water from overflowing the FT.