Backyard Aquaponics
A place to discuss aquaponics

The problem with letting too much gunk build up is the Biological Oxygen demand and the chances that anaerobic spots will form and/or gunk starts floating up and covering plant roots, suffocating them.

Best bet is of course to limit the amount of solids that get into the raft beds but of course there is little that can be done about the bits of plant roots and planting media and plant detritus that manages to get into the beds other than to clean them out periodically.

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Aquaponic Lynx
TCLynx Bought The Farm
Old Main System
Old 300 gallon System

I can't see any benefit of having media in rafts or FT's. Fine for the little aquarium at home I suppose.

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~2010/2011~
~2012/2013~
~2014~
~Backyard farming~

Back when I first moved to the farm, I wasn't planning to do DWC veggie growing. I build a "raft bed" shaped thing but I put pond plants in it. At the head of that bed I did have some gravel but again, It wasn't meant as a raft bed, it was for pond plants at that time.
Later when changing over to Raft production, I removed the gravel, it was pretty nasty which hadn't been a problem with the pond plants because they tend to use the ammonia up and having an anoxic pond muck buttom is really a natural thing for their environment. (NOT good for Raft veggie production though.)

I don't know how one would manage a "under gravel filter" for a Raft bed if it is bigger than say an aquarium. The reason we don't do such things in raft production is we want to avoid getting suspended solids all over the plant roots AND we need to minimize BOD in the raft beds since it is already pretty energy intensive and plumbing intensive to provide distributed aeration under the rafts even with relatively clean water.

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Aquaponic Lynx
TCLynx Bought The Farm
Old Main System
Old 300 gallon System

Ok no one's a fan then guess for good reasons

I was going to still use an air diffuser like this to prevent anaerobic spots
https://www.youtube.com/watch?v=eNMTUBtynSY

I was just thinking it could have been used as form of 3rd stage filtering system

I would keep all rocks/gravel out of dwc beds. Keep as clean as possible, aerate, and watch the plants grow!

Hi TC and of course anyone else reading in

Being relative new to this I would consider myself to be quite prone to having the occasional unc (uncoordinated) moment
While trying out a raft bed I managed to spill the entire contents of the bucket (that I was using to wash off excess dirt etc. from the plants before I put them into the raft system) into the raft water
In an effort to remove all the mess before it was recirculated back into the sump tank and further I used my Karcher pressure sprayer
I attached the Karcher and sucked out the contents into a wheelie bin for it to settle
The dirt in the raft bed was kept in solution (for want of a better term) by squirting the Karcher spray back into the raft bed from time to time
Once the bed was emptied to my satisfaction I allowed the bed to refill
I also used the time with the raft bed quite empty to Karcher off any algae on the tank walls as well
After 1 week to settle I transferred most of the water in the wheelie bin back into my system


Regards

Bon&Mark

Forgot to mention

My Hands and those of the Boss
touched very little water during the operation

Bon&Mark

I don't quite understand how you attached a pressure sprayer to empty the bed? Seems to me that spraying water into the bed would fill it further rather than emptying it?

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Aquaponic Lynx
TCLynx Bought The Farm
Old Main System
Old 300 gallon System

A 12 volt Jabsco water puppy pump, battery, 2 hoses, one for sucking and 1 for discharge. Portable and easy and fairly cheap.

Unfortunately, any one of my raft beds are way too big to be emptied into a wheelie bin or any other tank or containers I have on hand and empty at any given time. Been working on ways to vac off the bottoms without having to drain them but often that seems to stir the mineralization system enough that I wind up with escaped solids leaving the mineralization system to re-settle in the raft beds again.

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Aquaponic Lynx
TCLynx Bought The Farm
Old Main System
Old 300 gallon System

What about running the solids through Static Upflow Filter? Keep the solids suspended in the bed with a pump while you run the through the SUF. You'd probably have to flush the filter a time or two but other than that it could probably do it's thing without much input from you.

Some models of pressure washer will let you draw water from a bucket or tank rather than from a tap.

Drawing soil through a pressure washer style pump is not a good idea!

I use one of these for cleaning up my turtle pond, and the bottom of my AP tank. Put clean water in the garden hose fitting, it sucks up the dirt and sends it out the black hose.

I haven't tried this, but I can see no reason why this wouldn't work... Have a large container with some water and a pump in it, use this pump to run the vaccuum, and discharge back into it. Every time the dirty water goes around it picks up more dirt - far less wasteful!

That would require a static upflow filter big enough to handle the flow rate from the pump, AND require one that is set up close enough to the cleaning operation for the hoses to reach. And be high enough up to allow for cleaning it easily. I don't happen to have a mobile static upflow filter of sufficient size.

I suppose If I re-work a few things and pump down the mineralization tank a bit before doing the cleaning, I have a pond vac 4 that I can set up to send water to the mineralization system. I just need to be able to pump the mineralization tank down so that it won't start flowing back into the main system before I can let it settle. It just means I can't do the vac job when system water levels are high without wasting hundreds of gallons of water, AND I can only vac out a limited section of beds at one time before I have to stop and let things settle to allow me to pump off the clear water again.

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Aquaponic Lynx
TCLynx Bought The Farm
Old Main System
Old 300 gallon System

The flow rate depends on the amount of media and size of media in the SUF. The SUF in my RAS system filters about 300 gph with a modified 5 gallon bucket using K2 media. You can also divert the flow from the pump to stir the DWC. If I was doing what you're trying to (and didn't want to buy a really good vac), I'd probably just put the pump in the DWC, setup a manifold and have one or more 5 gallon bucket filters hanging above the DWC at the end opposite the pump so that solids are pushed toward the pump. How well this would work or if it would work and be convenient enough I don't know but if you have the parts it would be cheap to try making one and might save you a lot of time in the long run.

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5 gallon bucket, mesh pot lid (with openings small enough to keep the media in and prevent it flowing back through the inflow), 2 uniseals, 1 atrium grate to keep media from flowing through the outflow and a little bit of pvc pipe. The outflow could be a pipe capped with the atrium grate that then goes down through the center of the mesh pot and bucket. The inflow comes in below the mesh pot. The mesh pot itself traps some of the larger solids then the media traps the rest before the water flow back out.

With slightly different parts you could have the flow exit the top of the bucket through a bucket lid with holes or using an atrium grate through the lid. This might give you a better indication of when a filter needed cleaning by seeing reduced flow but might pop the lid off with too much pressure.

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