Backyard Aquaponics
A place to discuss aquaponics

duh

Hi i see you have smart pots there are they on fish water or neutrients

Fish water. My fish tank feeds into the smart pots.

Although sometimes I hook up an extra nutrient feed with chelated iron or trace elements.

Sorry to dig up an old post here, but I'm interested!

Suppose your "conventional" (if there is such a thing) aquaponics system has a particular sized grow-bed, say half the volume of the fish tank. Now, your typical flood & drain pumps a whole lot of fish water onto the growbed, but it all drains out pretty quickly (in a matter of minutes), so to stop the plants drying out you need to repeat the flood & drain cycle every hour or so. Each time you do this, most of the water ends up back in the fish tank. But the amount of filtration provided by the growbed must be proportional to the plant growth, as the plants are taking the nitrogen out of the system.

So, say you use a set of autopots such that the growing area is the same size as this "typical" grow-bed area (that's a LOT of auto pots). Then your system floods the autopots and has a freshwater inflow to replace it (eg a simple ball float valve). It needs this inflow because the water contained in the autopots will never come back to the fish tank.

All things being equal, it is my (novice) understanding that the nitrogen removal rate should be the same in both cases, because it is still proportional to the plant growth, and you have the same number of plants in each case. The only difference is that in the standard grow-bed design, you are expending large quantities of energy to basically pump water through the grow-bed faster than it can be taken up, whereas the energy in the autopot system is less as it only pumps as much as is used by the plants.

Am I stating the obvious here? I think so...

The problem with that is you have no bio-filtration to break down the ammonia into nitrates. If you added a bio-filter to the tank and then used the auto pots you could keep the nitrate levels under control. It would be similar to conventional aquaculture, ie replace a percentage of the water daily to maintain the desired quality, except that the water is going to feed plants rather than waste.

Nova

Jimmy, this is what I was meaning (from an earlier post in this thread).

Nova

Yes and no JimmyD.

Yes either way the plants take up only the nitrates needed for growth.

However the other purpose and benefit of an AP system using growbeds is to filter the water, not only of nutrients but of solids.

If you don't do so then the build up of nutrients and solids leads to excessive ammonia build up in the tank and dead fish... to state the obvious for any who don't know.

Autopots, by design, while removing the nitrates from the fish tank water do provide all thats necessary for the plants to grow. How effectively over time they may deal with any solid particles within the water supply without blocking the "smart" valves is a question which so far is unaswered.

However the autopots only use water (they do so efficiently) they don't return any water back to the rest of the system, so you would have to be constantly topping up your system with new water.

Effectively, by doing so, you prevent ammonia build up.... much like periodically cleaning an aquarium.... suppose to use the same anology the autopot is a bit like cleaning your aquarium and pouring the water on your plants.

However, just like an aquarium, you may need to filter the solid matter from the water before using it through the autopots....

One of the attractions for many people of an AP system with flood and drain growbeds returning to the tank is the fact that it's almost "closed loop", almost 95% water efficient.... the only waste/top up required is due to any water uptake by the plants, any lost through transpiration from the leaves back into the atmosphere or lost by evaporation from surface areas.

The other bonus of the growbeds is the fact that they trap and eventually breakdown any solids matter within the water... providing the plants with essential minerals and trace elements

Edited:

got to learn to type quicker

Really. the filtration isn't dependent on the number of plants you have growing in the system. A fully cycled grow bed will filter the water adequately if there are no plants growing. However the levels of nitrate will increase to toxic levels eventually and can either be removed through water changes or through uptake from plants.

The gravel is an exceptional mechanical and biological filter. Imagine if you had a 1:1 ratio of GB to fish tanks, you would have massive amounts of filtration given the pumps capacity is great enough. Compare that to indoor glass aquariums which can get away with relatively small cannister filters, a ratio of 50:1 tank to biofilter. The key with BAP is you can stock very heavily with a large filter.

edited: got to refresh the page before I reply....

It seems to me that both systems are about equally water-efficient, and if the pump cycle is honed as much as possible, the conventional flood & drain could be pretty energy efficient too. Plus as you say it provides the mechanical filtration.

further to what tm said, My take on the 2:1 bed:tank ratio is than all the media is not needed as a biofilter, but you need that "volume" of plants.

NFT pipes are a great example of this, in steve and anges system i used 20 litres of biofiltration with a total of 30 or 40 plant sites, enough to fill up oe of joels beds!

0 litres was probably a bit small, as the gravel does ANOTHER job too, it hold the solid waste unti it breaks down.

SO to summarize;

Gravel;

provides meida for bacteria to grown on / in
provides solids filtration / holding
Provides you with a convenient place to plant your plants!

Out of all of them the number of plant would be the one that conforms to the 2:1 ratio. (according to me anyway )

Gravel fish

Be a bite "rough" to eat wouldn't they?

:sigh: