Backyard Aquaponics
A place to discuss aquaponics

A Friend of Mine, John got inspired when he saw my big system and has decided to build a system.
This chap is a furniture designer and has a nice house in the burbs of Cape Town.

The concept here is that the system needs to look super smart as it is basically going to take up the whole of his front garden entrance way, incorporating a wooden walkway bridge over the water to the front door. and the growbed on the left. This is quite a cool idea as the walkway will provide shade for the water.

It is going to be a large volume of water and not such a large volume of growbed but he does not have his sight set on high stocking densities.

Of course he is totally visual being a designer and does not really have a clue as to the practical requirements of the system. That's where I (and all of you guys) come in. I recon if we can pull this off it may pave the way for many other system builds and possibly some money to be made. Who knows...

Anyway the first thing is to work out the design and make the practical requirements fit the visual design elements as he sees them.

1st problem is he wants the fish tank and the growbed to be more or less on a level. I think the growbed will probably be split between ornamental plants and vegetables.

I was suggesting we have a twin pump system, one in a recessed part of the FT pumping on a timer to a set or mabe just one big growbed. It drains via standpipe method to a, preferably not too huge, sump tank. Then have a pump on a float switch in the sump to return it to the fish tank.

The thing we want to avoid is having to much of a tide on the fish tank.

The other option is to have a big enough sump tank to flood the growbeds which then drain to the fish tank and then it overflows to the sump via a solids lift overflow and a solids swirl filter of some kind. Or it just drops the solids in the sump where they are then pumped to the sump or eaten up by crabs or something like that. Then we have just one pump which will be better.

Suggestions guys?

I will post some drawings as soon as I get them from John

What about slighlty raised grow beds which flow back into the tank/pond via a water fall?

Could use one pump then, especially if the growbeds are constant flow and gives the added advantage of not having to bend over as much to pick veggies.

Yeah as Arbe says, I reckon go for a constantly flooded bed. I found the other day that our 4 bed system at the shop has been running as a constantly flooded system ever since we put barra in the system about 4-5 months ago. I had no idea, someone had removed the timer completely, but everything has grown well..

Yep ! Absolutely ! constant filtration and one point of failure - can't get much better !

Ok. Yes that would solve all the problems but what about oxygenation for the roots and all that stuff. I am not sure he will want a raised bed but we shall see what plans he has in mind. With the constant flood does the gravel stay under water or does the water trickle through the media from the top down requiring a network of pipes to distribute the water?

The bed doesn't have to be raised much at all to get a cascade with strream going back into the FT. It oxygenates the water, looks cool and sounds great all at the same time. You could do it with as little as a 6" raise in level.

BTW, I vote for constant flood as well with the low level differential especially.

Ok. So with the constant flood the gravel is constantly under water. Do you not get an anaerobic thing happening in this situation? I was convinced the flood and drain was necessary to draw air down into the media for the sake of the bacteria and plant roots. Does constant flood rely on good aeration of the water using an air pump? Excuse my ignorance here but I have never played around with CF before. I am just trying to get my head around the aerobic anaerobic thing...

Constant flood doesn't require the media to be under water. You have the same setup with a bed with a standpipe and timer but you don't put a timer or a drain hole in the bottom of the standpipe. The bed will be constantly flooded to the level of the standpipe which you make 1-2 inches below the gravel.

Actually changing a timed F&D bed over to a constant flood is rather simple. Just flip the standpipe upside down so the drain hole is on top.

Yes the media is constantly flooded or "under water" except for the top inch or so, however due to the high oxygen levels in the water there are no anaerobic issues or root rot problems etc

Air pumps etc are a good idea for backup reasons but in my experience not always necessary purely for oxygenation. If you have water flowing and falling making bubbles it gets oxygenated anyway

The water level in the grow bed is set by the height of the standpipe.

Ok. So the media is submerged bar the first 15mm or so. But what I am interested to understand is why is this not an anaerobic situation? Does it rely on the dissolved oxygen in the water for the aerobic bacteria to exist. Kind of like an airlift biofilter but without quite so much air?

Sort of, yes.....

I must have misinterpreted you. I thought you meant the top of the media under the water. =) Yeah the bottom portion is constantly submerged.

In a normal flood and drain setup there is usually still a little water in the bottom that never completely drains. You don't get anaerobic zones there because that water mixes with fresh water during the next flood cycle. Same thing applies in constant flood. As long as fresh water is coming in there won't be any anaerobic zones.

Also note some plants love constant flood, others hate. There are quite a few threads on it.

We have progressed . the growbed is basically completed except for the drains that will be an bit of an issue. I have not been there lately so can't actually see in the pics where the drain from the growbed back to the pond is going to be. The problem with consulting is people don't always take your advice.... The wood structure which is bolted to steel uprights are for a decking walkway from the front gate to the front door. This will shade a large proportion of the fish pond. lilies and 'waterblomietjies' will provide more shading where the decking isn't covering.



any comments or ideas much appreciated

Looking pretty neat Brian......

Can;t really think of much to add...

I love this, always wanted a bridge over a pond. Is that some kind of bitumen paint to protect the wood?