Backyard Aquaponics
A place to discuss aquaponics

I started feeding my fish regularly and noticed fish waste on the bottom. Which I guess makes a whole lotta sense, but it surprised me because I thought most of it would get pumped in the grow bed for my compost worms to feast on. There was a lot on the bottom. When I scooped some up to see what it was, I disturbed a ton.

I adjusted the flow to send all to the grow bed without recirc. When I do that I can put 500 gal/hr through the growbed. Normally it does closer to 300. Fish tank is 150 gallons.

It started clearing up quickly, but the fish seemed stressed and a few flipped on their side to rub on the bottom or side of the tank.

I did an ammonia check and it came back 0.

Do I need to make adjustments to keep the buildup from happening? The pump sits in the bottom with the inlet about 1 inch high.

I could easily run a makeshift mop on the bottom every feeding time to keep it from building up so much again.

How is you system configured? What is the fish tank made out of? What shape is it? Most people design and plumb their system in a way which removes the solids by gravity, its called a SLO (solids lift overflow). Pumping from the bottom of the tank is risky; if you have a leak elsewhere in the system you will pump all the water out of your fish tank; obviously a disaster.

500 gal/hour is just over 3 times the fish tank volume per hour, which sounds like a lot, perhaps too much for solids to settle in the grow bed. What is the grow bed volume?

I think mopping up the solids on a daily basis is not really a sustainable solution. These things need to be designed and built properly so that maintenance is the minimum required.

Simple 1 tank, 1 grow bed flood and drain.

Fish tank is 150 gallons. It's a rubber stock tank.

Growbed is 200 gallons. 120 gallons when filled to the top of the standpipe. I estimate around 45 gallons water volume after accounting for media displacement.

Pump is rated for 700 gallons. Triggers the siphon in 8 minutes. So I estimate volume through the growbed is around 340 GPH, or a little more than 2x the fish tank volume. I can adjust that with the ball valves.

I was planning on doing an SLO or something similar when I add a sump and a second grow bed.

I agree I do not wish to mop up every day.

Something seems fundamentally wrong that the waste is collecting on the bottom

If you reorganise your pipe work so pump is in the middle of your fish tank and add a elbow to your return line so that you create a GENTLE water rotation the waste will work its way to the centre and most will be picked up by the pump.

I have one system like this

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My System
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Pump is also designed to work inline piping, so it would be very easy to add piping to the inlet and put the suction in the centre.

I don't quite follow the part about the return line. I have the siphon return splashing on top to help aerate. I think to do as you suggest, I would need to lower it down into the tank near the bottom and then elbow along the side. Is that what you mean?

I'd need to add another outlet in the greenhouse if I needed to add an aerator, but I oversized the whole circuit so I should be good.

Elbow for return so that it is flows in paralel to the side, as you say, but I don't think underwater, just above the surface of the water would be better, and is what I think Terra means. Otherwise you could create an accidental siphon.

I've tried a couple different configurations so far. This is what I have right now.

Not terribly thrilled with it.

It seems to do a good job keeping sediment in the middle... where is stays, less than a foot from the pump, just chilling at the bottom...

This definitely sounds pretty typical for a smaller, high stocking density system that doesn't have SLOs and a sump tank. I get solids accumulation a lot on single tank systems, and the relative amount seems to increase the smaller they get.

A thin layer on the bottom usually isn't much of a problem if you have good mechanical and biological filtration otherwise, but you have to be aware of how many solids have accumulated and will need to clean out the bottom of the tank if they start going anaerobic. It's also an issue I get with IBC systems sometimes because it's harder to get good water circulation in a square tank as opposed to a cylindrical tank, but you have the benefit of having a system with a cylindrical tank. In a square tank, you can't get water to flow into a vortex efficiently that would otherwise help direct solids towards the center of the tank.

I definitely concur with other peoples' suggestions when it comes to getting vortex flow going in your tank. Your best bet is probably going to be to move the relief line away from the center and stick an elbow on it. I would consider sizing up your pump as well so that you can push more flow out of the tank and through the relief line. Also make sure that the return line coming from a bell siphon is configured in such a way that the outflow from the siphon does not disrupt vortex flow within the tank. If you are able to get enough water pressure going through the relief, it may also be worth considering adding a venturi aerator as well to increase oxygen saturation in the fish tank - this should help reduce issues with anaerobic zones that arise from solids accumulation.

Another thing that will help is heterotrophs. Have you introduced red wigglers? They will help break solids down into smaller and smaller particles that tank longer to settle out. I also introduce Gammarus, a small freshwater amphipod that feeds on detritus. Ideally, a system should have many different species of small heterotrophic organisms in it - the kind that typically inhabit pond, stream, and river ecosystems. A biodiverse aquaponic system is a strong and efficient aquaponic system!

Hope that helps, good luck!

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I am always experimenting and always learning! Aquaponic systems engineer and plant alchemist. Farmer Educator at Ourfoods https://www.ourfoods.org/

My tank does have a couple squared off protrustions that affect the vortex. https://www.tractorsupply.com/tsc/produ ... l-capacity

You can see one on the front, and there is one on the back. That's why I have the circulation lines pointing both directions. Before I did there seemed to be a huge area of no flow.

Which line do you mean when you say relief line?

I do have red wigglers.

I think I'm kind of stuck with it for now until I can expand and add the sump.

Thanks!

Oh, your fish tank is oblong? It looked circular to me in the pictures you posted! The circulation lines you have installed already are a good idea, and you should still be able to increase water agitation and flow though even if you have a hard time getting vortex flow given the shape of the tank. Several airstones placed throughout the tank may help as well.

The relief valve would be the black spigoted ball valve that you are using to divert flow away from the main delivery line and back into the fish tank so that you can control the flow rate to the media bed. The relief line is the line this ball valve is installed on which tees off from your main line and drains back into the fish tank. I am not sure if other people use other terms for this plumbing feature, but this is what I have always called it. Every media bed system with a bell siphon I have ever worked with has one, and I use them sometimes to help control flow to tower modules as well.

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I am always experimenting and always learning! Aquaponic systems engineer and plant alchemist. Farmer Educator at Ourfoods https://www.ourfoods.org/

The fish are scratching/itching themselves on the bottom & side of the tank? is that still happening?

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No they seem happy now. Only when I try to clean the poop out and stir it up do they seem irritated.

That's good.
Fish also behave like that when they're ill/sick,may have parasites.

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Anyone know of a place to get a good circular aquaculture tank in the US?

The ones I see online in the 100-200 range go for north of $500, which is why I'm using a $100 livestock watering tank. Trying to save some $$$. Maybe I'll keep an eye out on craigslist.

I tried using one of these to remove the excess feces:

https://www.amazon.com/Aqueon-Medium-Si ... 154&sr=8-9

Since my fish tank is half buried in the ground, I only have about 18 inches or 45 cm between the top of the fish tank level and the bottom of the collection bucket, so maybe not the strongest siphon in the world, but...

Even holding the siphon right over the fish poo it barely moves. It’ll swirl a bit in the inlet and then fall back down. That is some dense fish poo. They look like rabbit feeding pellets. Is that normal?