Backyard Aquaponics
A place to discuss aquaponics

hang on, doesn't the UVI system have a biofilter?

hummm.....think you're absolutely right Steve.....the old solids removal problem.....

they remove large solids, then use bird netting scrunched up in a tank to trap finer particles, this would act as a biofilter to an extent, but it's only quite small, they don't have a classic biofilter like some systems I guess..

There was a place in Queensland where they were doing some trials at a TAFE or UNI, they seemed to only be using rafts floating on the surface of the fish tank.

OK. The roots would definatly house bacteria, but i wonder the ration to the "biofilter". I should know this, but are they running high density?

I asked James Rakocy about this when he was in Brisbane last year and he advised that it was the bacteria on the rafts that were providing the biofiltration, not on the roots, because the plants are harvested quite rapidly and would not have the time to get the populations required.

i guess they have a fair run for rafts.................

It may be that they do not add the roots ability to house bacteria to their calculations because it's not a constant, but the surface area of the rafts are a constant? I agree though, that it must be a huge raceway for the rafts for the Styrofoam surface area to be able to work as part of a biological filter!

BUT, I think we all agree that to have this type of density of fish in this small of an area, that there would have to be some type of solids removal and biofiltration in place, if the ONLY plants were to be in a raft system floating on top of the fish tank, right?

Personally, I think having the rafts on top of the fish tank is a great idea for additional grow bed areas. But IF space is the issue, then I would go with either a vertical or horizontal pipe system filled with gravel. Then the gravel works as the solids removal and biofilter area.

On a side note, would the fish eat at the roots of the plants in a raft system? Obviously, it would depend on the type of fish, but if they did, wouldn't they kill the plants? Or are there species that wouldn't eat the roots? I may go to adding rafts to my later system with my crays, because the crays wouldn't be able to easily get to the plants and roots.

Tilapia would consider a raft system to be their personal salad bar. They would love the roots, thank you.

Yes they do have a huge raceway, but remember also that styrofoam ends up absorbing water over time and maybe as it does this the surface area available for housing the bacteria is also increasing. Personaly I dodn't trust styrofoam as product for use in my system - but as you all know I'm pretty anal about that sort of thing.

if i could be sure the styro i got had NO fire retardants i'd be happy.

I think all building styro has to?? not sure.

no fire retardants Steve? .sorry!

you lost me!

what did i miss?

FIRE RETARDANTS! are we the only pyromaniacs in BYAP ?

If you're doing a raft system, you should consider floating the raft like a catamaran so to maximise the water surface area for oxygen transfer.
Also when I did a little raft hydroponics some time ago, I used paper towels to lift the water via capillary action which was enough to water the shallots I was growing, until their roots could touch the main water surface. However the papertowels must not be allowed to dry out, they could get wet and stay wet, but if removed from the water, they would lose their capillary ability. I would expect significant bacterial activity to occur on moist towels in an AP system, with matching reduced life span of the capillary medium.

Another point, some plants like wet feet more than others, maybe you should grow tomatoes first.