Backyard Aquaponics
A place to discuss aquaponics

Hee Hee I am fool! LMAO!

Hi Joel
One of the many incarnations of my original test system had something like what your talking about. It had to be super low tec and energy efficient a 700l tank made out of starpickets fence wire shade cloth and black builder plastic very easy sturdy cheep to make and as long as you want. The pump was / is (i dont use anything else) a washing machine pump. grow bed(styrofoam box) perched just above and draining/ overflowing into tan. For a while there i had it with just an overflow, when the timer kicked in the bed would flood and overflow into the tank when the pump stopped the bed would drain back through the very high clearances in the washing machine pump (those suckers wil pump a 5c piece through without blocking) so in essence flood and drain through only one pipe and no fittings just keeping the pump the lowest part of the system as they dont self prime. Total pump head was about 300-400 mm. from that system we currently have a styro box with a giant tomato plant , some Ibeka and 3 huge basil plants the kids counted the ripening toms and we got to 97 set and ripening fruit and many more to come.

So yeah it works and its easy( ps dont forget im the one using quite a bit of liquid gold so that may be a big part of the success.

Cheers TimB

Same idea but instead of a header tank with floating raft have two sets of grow beds.

Tidal growbed fills slowly and empties quickly. The header growbeds are standard F&D fill quickly but drain slowly.

Would make an interesting experiment to see if there is any difference in plant growth.

We were discussing it here too: http://backyardaquaponics.com/forum/vie ... c&start=60

Basically it complements a flood and drain setup. As the tank empties from water going to the growbeds, the side GB's empty, and they fill up again as the water is returned.

I don't know if I could drill holes in my new tank or not when I get it.

just a thought, in the traditional flood and drain the water always enthers the bed from the top and exits from the bottom, trapping solids somewhere in between. During the set up of steve and anges system we smoetimes made the flow too quick into the gravity drain bio-bucket and i noticed that some of the solids would "float" back to the surface. As the water flow would be bottom up during flood and then drain during the "low tide" might the solids not be trapped as well?

Give it a go though!

Interesting idea!

The amount of water in this system is critical. If the total volume of water is decreased, the flood level of the grow beds reduces, too.

Other than topping up to a pre-determined level each day, how do you propose to maintain the tank volume at the correct amount? Initially, I thought of using a float valve but upon further reflection it's not that simple.

Simply..... A water sensor and a pump in a water reservoir. Setup to automatically top up the fish tank.

i think the problem is that the whole thing floods and drains so the sensor would have to be in the header tank and be on a time based limit as well. IE if the sensor is not triggered in a 10 minute period then add water.

Or the bleedingly obvious method, the one that i currently use..............use your eyes (which gary did mention)

Had a thunk.

It might as simple as a float valve but then its not.

If you running an external pump like F&F does then its just a float valve. The pump kicks for x minutes and removes a set amount of water from the FT. This will lower the water level in the fish tank a certain amount. If that amount lowers the water below the level of the float valve it will open topping the system off to the correct volume of water in the whole system.

This won't work in a simple manner if you are using a submersible pump with a float switch. If there is not enough water in the system then the float switch won't get high enough to turn the pump on.

To get it to work with a submersible fit a small tank to the F&D grow bed that is quickly filled when the grow beds nears the top of its flood and then drains slower than the grow beds drain. Then fit the float valve at the bottom of this container. If there is enough water in the system then the float valve will always be off because it will be refilled before it empties enough to open the float valve. If there is not enough water then the float switch will not get to a sufficient height to ativate the submersible pump. While the pump sits idle the float valve container empties until the float valve turns on. It will then top off the system until there is enough volume in the FT to activate the float switch starting the system cycling again.

Do I get away without pictures?

Nitingales have float switches very cheap

Been thinking again.

For such a system to work (tidal grow beds and f&d growbeds together) there must be a number of F&D growbeds sufficient to take the water from the FT so that the tidal grow beds will completely drain.

The main advantage that I see of this sort of tidal system would be that it could limit the change in water level of the FT to the fill depth of the tidal grow bed and would lessen or eliminate the need for a sump. For that advantage to be realised the Tidal GBs and top 27.5cm of the FT must be balanced with the f&d GBs.

example
Take a system based on an IBC FT, similar sized GB (in terms of footprint) and assume pipes don't add any volume to the system.

V1 = Volume of water in the top 27.5 cm of FT.

V2 = Volume of water required to fill Tidal GB to a depth of 27.5cm.

V3 = V1 + V2 = volume of water required to empty FT and Tidal Growbed
= Volume of water required to fill f&d GB

G = Void % in gravel to be filled with water (45% in the gravel I've measured)

A = Area of f&d GB that is filled to a depth 27.5cm and is required to balance system.
= V3/.275/G

V1 = .275 x L x W = .275 x 1m x 1m = 275L

V2 = .275 x L x W x G = .275 x 1m x 1m x .45 = 123.8L

V3 = 123.8 + 275 = 398.8L

A = 398.8 / .275 / .45
= 3.2m2

Hope my reasoning is sound and that it makes sense.

I think it holds some promise as being one of the most efficient methods of AP with some thought and testing.. You can double your growbed area/volume while still using the same pumping power, in a sense the bottom growbed is free...

Forgot about that plus.

Can anyone think of any minuses?

So far all I can think of is that the water entering the Tidal GB would be moving quite slowly and might not be oxygenated very well in the process. Might increase the need for areation which would decreae its improved effiency.

Also you would be limited to relatively flat sites or small nodes on a sloping site.

Someone said that there maybe an issue with solids collecting in the growbed. It can easily be solved by including either a false bottom 1 inch or a very coarse media ie Broken pots in the bottom of the growbed (or where water enters). Most of the solids would in fact be sucked back out when the water drains. A drain in the bottom would work best imho.

I am sure this would work well for NFT channels as well as long as the water level in the tank is fairly constant. Or why not hook NFT pipes horizontally along the edge of rectangular F&D growbeds. Same concept as with the tank.

That was Steeve. I thought we wanted the solids to collect in the GBs
Isn't that the best spot for them ie not in the FT, SUMP, NFT or any where else?