Backyard Aquaponics
A place to discuss aquaponics

I`ve been into tropical fish for a few years. Somewhere along the way I learned about and built a fluidized bed filter. What this consists of is a sand filled length of 4" pvc pipe capped on the top and bottom. It has an input and output pipe. A pump in the fish tank forces water in at the bottom and out the top and returns to the tank. A valve in the input line adjusts the pressure so that the sand is just fluidized ( like quicksand). Too much pressure will wash the sand out and not enought will halt the water flow. It`s a little hard to start and adjust, but once you get it going it makes a great home for the nitfifying bacteria. I ran a 30 gal. crowded tropical fish tank for a year without any water changes with no lost fish and crystal clear water. and never measured any ammonia. This requires a particulate prefilter btw, the gunk will clog it up eventually if not filtered out. Supplementing the water with air will also be needed due to the bacterial consumption of oxygen. Aquatic plants did the job in the fish tank. And they grew like weeds !
This seems like a better solution than separate water and medium filled growing tanks if youre limited in space ( like me). Theres still the issue of keeping the plants out of the water if using a single tank but I`m sure there is a solution.

ZKT, Sounds like a nice place for the bacteria to grow, as in getting setup to seed another AP system. The sand filter could be moved and connected in line with a new system and used to seed its bacteria.
As far as (a beter solution than seperate water and medium filled growing tanks), I don't understand. Where do you plan on growing the Veggies?

roots in water- everyuthing else above

ZKT.....as someone who is interested in discovering new ways of doing things (rather than just sticking to the one old re-discovered way) I found your post on sand-filled bio-filters interesting.
While I agree that gravel beds will function as fluidized bio-reactors, and I can see the other benefits in having gravel grow beds (cheap, simple and proven), I can also identify situations where having a couple of tons of gravel (or more) in the equation might not suit everyone including:

- if you've got your system inside.
- if you're physically incapacitated.
- if you're thinking of doing aquaponics commercially

Bio-filters (whether they be trickling bio-filters or sand-filled fluidized bio-reactors do the same basic thing that gravel growbeds do - they facilitate the conversion of ammonia to nitrites and then into nitrates. As for how we use the nitrates - the sky's the limit.

Solid removal is the other challenge.

Vb raises a valid point, the guy with the commercial setup in minnamurra, which i'd say is currently running at below to the same capacity as EB's sytem has a swirl seperator and a mesh filter. Both the swirl seperator and mesh filters need to be cleaned out daily. Where as becasue the gravel beds are the solids trap, and they flood and drain continuously the solids are always exposed to atmospheric oxygen and break down as part of the system.

But i do see your point GD, a tonne of gravel may not be ideal in certain cirumstances

Daily? Ithought it was twice daily at current stockinglevels and one every 6 hours at full capacity

I tried to incorporate the "apparent" solids load.............Sorry guys, only a few people will get that one.

But in all seriousness Monya is correct with his values.

Steve

Is what you describe a vertical lilter that pumps the water up? Can you post a picture? What sort of filter did you use to remove the solids? I assume that a bucket of sand would have a greater surface area than a bucket of rocks and therefore you would need less of it?

Monya, do you want to have a go at describing the swirl filter and the mesh filter? and also a description of minnamurra? I'm still catching up on posts

Give us a second KE14

I am not technical minded but here goes.

At the bottom of the swirl seperator, there is a tap which allows them to drain the fine particulate matter that has collected at the bottom into a bucket.

The water was gravity fed out of the fish tanks and through the mesh screens (not unlike flyscreens) which were cleaned regularly by lifting them out and hosing them upside down over a tub.

It was then gravity fed into a sump where it was pumped into these cylinders which acted as the biofilters. They were filled with bean bag balls.

They also acted as header tanks to gravity feed to the greenhouse

So, with the solids removal done, and the ammonia-nitrite-nitrate convesion happened, it was off to the polytunnel for finishing and removalk of nitrates by the plants

Finally, gravity fed back to the fishies

For the tech side of it, I would needsome other input. Like was water flowing through the swirl seperator at all times Steve? I sort of lost them there. I got the impression that it was bipassed as required.

Anyway, hope this run down helps.

Thanks Stu!

I can't remeber hearing about the swirl seperator being bypassed, only that they had the capability of bypassing any componet. I'd assume it would run 24/7