My first system: Raft converted to Chop Charcoal Media Bed

[Paul Letby]

Hey Gang!  Thought I'd share my setup with you.  It's not pretty but it works.  I chose to enter aquaponics to keep my water change bill down as I was 'fish sitting' this winter.  My neighbor needed somewhere to keep his fish after he closed his pond so I agreed, seeing as I had a 30 gal tank with almost no residents.  I never saw more than 10 goldfish at a time so I figured I was good. Not so.  His water was so full of algae that I never saw all 60 at once!  That put me into emergency mode and I dragged my 55 gallon rainwater barrel into the basement and set up a filter with powerhead. 

After the two tanks cycled I realized that I'd have to do water changes very often to keep nitrates down.  Then I thought about aquaponics!  I'd seen the idea before, but never really considered it because an outdoor setup around these parts would only run for maybe 4 or 5 months out of the year before freeze up.  I did have a light stand in the basement with the barrel though.  So I chose the raft system simply because I had rafts on hand from messing around with hydroponics last year.  I grew lots of lettuce, but didn't like flushing old nutrient down the drain.  Now I don't have to worry!  I built the GB out of lumber with construction poly as a liner, ran some plumbing from the barrel to the GB, found an off season pond pump at the local home improvement box store (75% off!) and rigged it up to pump back into the FT.  Drilled lots of holes in foam to fit pudding containers I drilled more holes in and filled them with gravel, plopped them into the holes in the foam and plunked seedlings into them!  Confused yet?  I am.  Plugged in pump and watched!

Oh yeah, almost forgot.  To keep nitrates down in the 30 gal fish tank, I used some previous experience with aquatic plants to handle that.  4 weeks ago all my aquatic plants in there were just sprigs, except for the sword plant, but it's grown alot too.  I mixed up my own fert (micronutrients, P, K) so that the limiting nutrient would be nitrogen, and so far so good.  Only have hard scale algae at present, and that's very slow growing.  I'm not sure if I need the CO2 injection with so many fish.

Nitrate is almost unreadable for a few weeks now in both tanks.  It was quite scary high before the plants got going. 

Anyway, here's some pics for it all to make sense!

Here's an overview of basement system:

Lettuce view:

30 gal tank upstairs at feeding time!

[Jack belcher]

Hey Paul,

great thread! seems to have been going a while...

The thought occurred to me awhile back to use charcoal (or biochar) as a medium, but i thought it might float off, or cause the pH to rise.

Since you have tried it for a significant period, I have a few questions for you:

How long have you had the charcoal bed running for, and have you had any negative issues with it as a medium?

Have you noticed any specific benefits, ie pH buffering, nutrient regulation, increased microbial activity, water cleansing, faster breakdown of solids.

cheers,

Jack

[Paul Letby]

Hi Jack,

Thanks for your interest. 

Charcoal does float around when you first put it in the bed but only for a few hours. 

My setup has been running for two years. 

There are only a few negative issues: It wicks water all the way to the surface, so it's always wet which leads to high evaporation.  See pictures of moss. It does tend  to be rather fragile, so small bits make it into the sump.  If you have a small pump it can clog over time if you don't check it once in a while.  Now that I have a bigger pump I can't see this being an issue as charcoal is fragile and that monster will just eat it.

Benefits?  Well, I have nothing in my experience to compare it to, though the water was completely black and opaque when first started up, within a few hours crystal clear.  I don't think it necessarily has those properties anymore, but the water is always crystal clear.  Can see to the bottom of the barrel no problem.  My composting redworms love the growbed, actively munching any dead roots or anything else thats rotting.  I have a hoard of springtails that do the same thing.  They're funny.  Supposedly related to ants, they hide from the light but come out at night.  When the lights first come on they're all over, then quickly make themselves scarce.

Hope that helps

Paul

[Jack belcher]

Hey Paul,

cheers for your quick reply.

I saw the moss, nice touch! Did you put it there or did it just arrive...? lol

what size gap do you maintain between the max grow bed water level and the top of the media?

do you think if you increased that gap then it would stay dry? or you could top dress with gravel of some sort.

I've never heard of springtails, but i will look them up. Composting worms are an AP system's best friend!

Do you use oxygenating plants in your fish tank? i was thinking about the benefits of including them in the system.

also duckweed is useful as you can use it to help close the system...

Cheers again..

Jack

[Paul Letby]

Hey Jack,

I think the gap is around 2 or 3 inches.  I don't think it would stay dry unless the gap was very large.  I am saving up for some expanded clay pellets to top dress just for this reason.  Then I would have that ideal dry surface I'm looking for.  I might reserve a small spot for moss as my Honey likes it.

I don't use plants in the fish tank as I'm using a 55 gal rain barrel at the moment.  As long as you had enough nutrients for both them and the grow bed I'd say go nuts.  I have run successful Dutch planted aquariums, and I'm not interested in that kind of maintenance anymore.  It's pretty cool watching streamers of O2 though.

Duckweed.  I have a love/hate relationship with it.   As of now the hate side has won and there is none about.

Paul

[Paul Letby]

Here's a close up picture of springtails.  I held a magnifying glass in front of my phone. :) They don't like the light so I took this right after the lights came on in the morning.  You don't normally find them out in the open like this.  They tend to get too close to the bell siphon and end up in the sump floating on the surface.  They seem quite happy down there.  I've had them survive for years on top of the water in a 75 gallon fish tank.  I suppose they feed on any rotting material they find on the glass/water interface.

[Jon Parr]

Wow, that's a really great pic of springtails from just an iPhone and a glass! 

Paul, I may have missed it in the thread, but what was the initial and long term effect on pH from the char?