Growbed size/depth

[Pat James]

 I have read and looked at many systems and many seem to prefer a foot or so depth. Is there a reason for this in raft beds? I split my IBC totes so they are about 19 inches high. I need to leave room for the rafts, plants etc, but why wouldn't I want as deep as possible?  Seems to me that more mass of water makes for a more stable environment.

In my case, where I am using a swimming pool as fish tank, I have more than enough water mass. But i plan to keep a few of my beds full and maybe keeping minnows or fry in them. Some are going to be modified raft beds where they fill and drain but with the growing deck suspended at some specified level. Those beds might have some crawdads as scavengers.

Both types of beds will have some material in the bottom as media, but not nearly enough to plant in...probably just an inch or so along the bottom.. I have been saving plastic hospital waste from the operating room.

[kl kingston]

Hi Pat,

You mentioned ..." modified raft beds where they fill and drain"  and ..." some material in the bottom as media, but not nearly enough to plant in". 

Why drain and flood a raft ? Why have media along the bottom ?

The people at Friendly Aquaponics use 12" deep rafts, and have directions on their site to build their own version, including paint and specs. No pictures, but the instructions are great. They grow lettuce, lots of it, for Costco, in rafts on their working farm. Check out their weekly blog. They have been doing this for awhile, and this is their livelihood, along with classes at their farm in Hawaii. I have learned quite a bit from their approach...this works and this does not work, for these reasons. I find this helpful.

Lilypad Farm, here in Texas also uses floating rafts. They grow 2 kinds of kale and 5 kinds of lettuce, along with various herbs , year round. Their farm is also a working farm, and they sell live food, that is, roots intact, at farmers markets, and other places.Apparently they sell tilapia as well.  

Meg Stout, at 365 Aquaponics , uses 50 gallon Rubbermaid tanks for her floating rafts and has made several  video tutorials for aquaponics building projects.She has made several youtube videos about the deep water raft approach, definitely deeper than 12 inches.

The people at Taiwan Aquaponics use floating plastc rafts in a constructed pond maybe 3 ft deep with prawns.Nice video on youtube. The pond is not full of rafts, and you can see this in the video as the children push the rafts around in the pond.This is a perfect fit, as shrimp are detrivores, and  this is how they survive in the wild. 

Travis Hughey has a great  tutorial for his Barrelponics system, available for free. He uses blue plastic barrels and gravel for his flood and drain media beds. Great guy, and very helpful.He has a yahoo group, and this low tech method is part of his ministry in developing countries, helping people feed themselves. You can find him on google. His approach is using what is readily available all over the world. Very minimalist, and very effective.He also sellsproduce from his systems to local restaurants, and gives some of it to charity.

Have you seen Murray Hallam's videos ? He uses media beds and has a food forest in his greenhouse. Lots of helpful info

There are as many ways to build a system as there are people, and no right or wrong way to do this. Some things work better than others, and aquaponics involves troubleshooting and problem solving. You will discover this for yourself, and find what works best for you. As long as the fish are happy, the plants usually adapt. There is a sort of homeostasis as the plants and fish seem to strive for the same goal.

~~KL in N TX

High Antler Farm

  

[Pat James]

Kl, The reason I have been trying this modified version is that I am trying to add as much oxygenation without using a separate air pump.

I have a couple separate bio filters, but this is small considering my water quantity. The small amount of media is to trap as much of the detritus as possible.

Since the original posting, I have made a couple discoveries. One of which that it takes a fair amount of time to fill a 1/2 IBC tote with a 3/4 inch line. The suspended raft can actually dry more than one would want...and the days are not even hot yet.

[Bill Bailey]

Just my thoughts on your question. We all think of and try different things, we have to because of outside system parameters, But the few things that do not change are the Chemistry of Main Fish Tank, Requirements and Chemistry of food to plant roots including Oxygen, If you keep your roots in deep water for long periods of time the roots will fail to get oxygen and drowned. If you add minnows and crayfish they are going to have a high mortality rate in Eb and Flow system, and you will be damaging plant roots with Ammonia as well as returning Ammonia and Nitrites back into you main Fish Environment. As well you could actually plug pumps.

Good luck 

[kl kingston]

What size airstone are you using in your raft?

You might get a couple of them on your pump with a 'T' connector.There are several sizes, some rather large. That will add some oxygen to the roots.

After adding the raft and plants, your IBC 19" depth is 16", more or less? That should be plenty deep for a raft system.

 Composting worms in the media bed eat some debris and waste, but not all, while adding some of their own waste. The slimy coat on the worms destroys chitin, bad for shrimp. For this reason, our worms are in a separate bed.  

Pat James said:

Kl, The reason I have been trying this modified version is that I am trying to add as much oxygenation without using a separate air pump.

I have a couple separate bio filters, but this is small considering my water quantity. The small amount of media is to trap as much of the detritus as possible.

Since the original posting, I have made a couple discoveries. One of which that it takes a fair amount of time to fill a 1/2 IBC tote with a 3/4 inch line. The suspended raft can actually dry more than one would want...and the days are not even hot yet.

[Pat James]

@ Kl... I have 14 grow beds. Each are 1/2 of an IBC, so about 1500 gallons of water. That would require a pet store size oilless style air compressor. Years ago one of those used to cost $400 or so... No idea what they run now. I am using the "splash and circulate the water" system.

The only reason I am not going with media filled flood and drain beds is that media (even cheap gravel) is also too expensive to buy and have delivered right now...