Backyard Aquaponics
A place to discuss aquaponics

I've read that it's bad to pump out of the fish tank as the water level will fluctuate. My grow beds are above my fish tank, so I can't use gravity to flow from the FT to the grow beds, I have to pump up to the grow beds.

Yesterday, my neighbor told me she has an unused jacuzzi tub (probably around 100-120 gallons) that she offered to me for free if I can use it for my project, and I am thinking that if I put my pump in the tub, and put the tub on the ground, it will be slightly lower than the fish tank. The tub would then become a "sump" but it would exist after the fish tank, instead of before it. The grow beds would drain directly into the fish tank and it would then overflow / gravity feed the tub.

My fish tank is 500 gallons (1900 liters), and sits on a concrete pad. the water level will be about 28" above the concrete. The jaccuzi would sit on the same concrete pad, but it is shorter, water level would be about 22-24" above the concrete.

My question is, can this configuration work? What type of considerations should I account for? I'm assuming that a jacuzzi tub would be fish-safe, since they're usually acrylic or ceramic coated fiberglass and are designed for humans to sit in.

Hi
Simple answer is;Yes.
CHIFT PIST: constant height in fish tank, pump in sump tank.
BUT
You may want to consider adding a SLO. solids lift overflow.
This will lift detritus from the bottom of the Ft and move it to the ST.
You could also consider adding a RFF radial flow filter in the line between the FT and the ST
Aint life wonderful! you have a great neighbour who gives you a gift.......... and just a little bit more construction work!

Great. Does a gravity feed provide enough velocity to make a SLO and RFF work?

EDIT: And, do I want a larger pipe, same size, or smaller pipe than my pump input/output?

Hiya cathode. There is no problem having the pump in the ft. Sure it's not ideal, the ft fluctuated and the fish waste is masticated but this is not bad, many systems operate successfully this way.
Having said that could you raise the jac tub 30mm(12") higher than the GB? If so perhaps use the jac tub as the ft and the existing ft as the sump?
And yes slo's and rff's work well gravity fed. Have a look through the members thread for systems similar to yours and see what pipe size and configuration works for them.

..
but the biggest issue is IF something goes wrong.. or rather WHEN something goes wrong..
You can think through EVERY possible failure that could happen.. from burst pipes, objects blocking pipes, etc.etc.

PIFT (PumpInFishTank) has been done, by raising it to a fail-safe level, but then you don't lift the muck that you need lifted..

Plus 1, to trying to arrange CHIFT, and let gravity do it's job..
..
.

Having your system set up like you have it is fine.... Almost every system I've had is set up like that with the growbeds above the fish tank and no sump tank. This story spread around that fish don't like water level fluctuations is a complete falacy.

I designed my first system like that FT SLO-> ST pump to GBs Drain to FT. Works perfectly well!

The water level in the FT still fluctuates, that isn't a problem unless it is a huge fluctuation, and that can happen when pumping from FT to GBs where the relative volume of water removed is large. With my system, leaking pipes, failed pump etc are not an immediate problem- the FT stays full, and the air is always on. With a pump in FT, if you have a pipe failure, you can pump your FT dry, so you need to be sure your pipework is failsafe.