Backyard Aquaponics
A place to discuss aquaponics

Hi All,

I'm looking to setup some "dirty" wicking beds, in that they wont really be beds, more using multiple large pots as wicking beds.

I have the pots and i have approx 60l of pumice (30-50mm) and then multi purpose compost, and will be using weed membrane as a separator.

A couple of questions i need help with:

1) the overflow pipe - does it need to be at the top of the pumice layer,or just under the top?
ie should the water be touching the bottom of the soil, or should the soil only touch the weed membrane, which will touch dry pumice?

1b) does the pipe inside the bed need to be at the top, if the outlet is higher? (there is already a hole in one of the pots, but its low... can i just use the existing hole but have the overflow higher to correct the water level?


2) is pumice sufficient as a wicking material? or do i need to put some form of other wicking material from the bottom of the pumice to the soil?

3) is a copper pipe/brass fittings ok to use on the water overflow for growing veg?

This should answer your first two questions - I would put the overflow pipe below the top of the pumice layer. I would connect an elbow and a riser to the overflow pipe as it exits to the outside of the wicking bed. You can then change the water level by changing the length of the riser that is on the outside of the bed so you would not glue the riser and you want the parts to be snug without leaking. This means that you can use the existing hole and use the overflow riser on the outside to set the water depth inside. If you set the overflow pipe within the wicking bed low enough you can remove the elbow and riser and drain most of the water out of the wicking bed when maintenance is required.

I'm not sure what you're asking on the second question but pumice will be fine as a wicking material. You'll have to adjust the water level to get enough moisture to the bottom of your soil.

On number 3 - Never really checked into this but I suspect it's OK, I used PVC since it's simpler. If the outflow is going somewhere like back to the fish tank then I'll suggest doing some additional research to see if there is likely to be any issues with toxicity due to the metals.

Hope this helps.

Thanks for the info Scotty,

I have an old cold water tank that is used in the uk, which i want to repurpose.

The copper fittings are from that system - i cant undo them (as in they are stuck!) so was considering reusing. However i dont think they are water tight anymore so i've ordered some 40mm tank connectors from a pond/aquatic supplier. I will cut out the holes with the existing fittings and use them to create the adjustable height as suggested.

overflow is going into my lawn so no problems with reusing.

Thanks for the info, will get on with it this week once the fittings arrive!

I've started the first bed, photos attached.

I put a crate in the bottom to give some more volume, and then the rest is filled with 30-50mm pumice stone.



So far i have two problems,

1) there is a slow drip from either the connector or the pipe going into the tank connector

I've tightened the fitting (though getting a spanner for 57mm is a bit difficult! i've had to resort to using a g-clamp to make it as tight as possible, next i need to use some ptf tape on the grey 40mm pipe and then push it in the connector - hopefully that seals the dripping!


2) the weed-proof membrane appears not to be so good at wicking!

I ordered another type, however a test on that doesn't seem to make it much better!
So I've resorted to testing samples with a couple of glasses of water to see how things work before i put them in - i dont want to have to take it apart later + still getting some night time frost so no point putting seedlings out yet.

My take on it is the stone is to largere move that and just fill with potting mix all the way also starting off you need to water from the top till the roots get down

I've only made a few wicking bed type containers, but I've had success using cups or pots that have holes in them, with fabric inside, preventing the wicking material from falling through the holes. This extends down into the reservoir area, and the soil makes contact with it on the top. A tight packing helps the wicking action to happen. I've used sand, smaller size perlite/ pumice, and coco coir. They all have worked well. That is some huge pumice. As F&F mentioned, that might be the issue. Being that big, there are probably too many gaps in between the stones, preventing wicking from happening.

Don't get overly concerned, all these methods will work and if not you can add some other wick through the landscape fabric. You can also raise the water level up to the bottom of your potting mix. The idea about using the potting mix for you fill is probably the best since you don't have to separate as many components if you tear it down. You might lose a bit of water reservoir volume but this shouldn't make much difference.

Thanks for the feedback guys, so i found some other material which is better at wicking on its own, did a simple test - two glasses, one on the sideboard, one in the sink. Ran the material between them... couple of hours later, the sideboard glass was empty and the sink one was filled - so i know that material will do the wicking for me for this bed... I've put it in the tank and will see if it stays wet though today, if so, i'll top it off with soil and its ready to go...

For my next bed, you three believe that the pumice is too big? if i make it smaller, then use the membrane do we think that will work? The membrane itself seems to not wick at all on its own - i redid the above test with a small sample of the membrane, the length was soaked in the full glass, then one end drawn out and into the lower one... a little bit of water came into the lower glass (probably what was already on the membrane) and then nothing further...

I have no access to any more crates at the moment (and in lockdown due to covid-19) but looking to use some waste pipe as the space for the second...

So wicking sorted, the pumace in this case hasn't done much other then provide space for the water to sit, while providing a solid base for the soil...

The leak is still there on the elbow - no ptf tape to be found, and i cant go and get some - so duck tape for now will have to do!



The next task, what to fill it with!

I have

Well rotted manure,
multipurpose compost
clay soil in the ground!

Should i mix the multi and clay and add the manure on top?
Should i mix all three?
should i only use multi and manure? mixed? separate?

My opinion, i wouldn't add clay to raised beds. I have just spend weeks reworking my mother-in-laws raised bed, that they added clay to reach volume. Most things rotted off when it became saturated. I would alway start with the other two. Even if it only fills to halfway. Then over a year or so top up.

Mixed together or layered?

if layered, which one at the top?

What you want is a mix that wicks up water but still preserves some air spaces. Perlite usually helps with the air spaces.

I'd mix together, add some topsoil if you can get it to bulk out the mix. Even if it is an inch or so from the ground under the wicking beds.

As you mentioned top soil, just reminded me I have a third of a cubic meter of it since I did the drive four years ago ! Just taken a handful to test it's wicking abilities... And filtered out the stones for a small batch so will see what happens.

But looks like top soil, farmyard manure and multi-purpose will be the mix, task for tomorrow, and then wait for the weather to not be freezing overnight to start planting...

Once that one is sorted I can so the other...

Got some small pots to do as well for single year planting if my strawberries germinate!!!

Filled the tub up with about 10-15 cm of topsoil and multipurpose - left it overnight, this morning all the soil is wet so seems to be working...

Going to mix some manure into some more topsoil and multipurpose and fill up a bit more and then plant a few seeds... see how we go!