Backyard Aquaponics
A place to discuss aquaponics

JP, Do you have your RSG just flat on the bottom of your growbed, or notches cut into it? Pretty handy that your able to control your nitrates so closely. Haven't had the need until winter came and some fish went inside. Most impressive!
No CI added since the nails?

Notches in the bottom edge to help aid water flow downward.

I actually have still added CI every now and again. Of course since I don't have a control, I don't know if I would have been adding more without them.

Wish I had more space for parallel systems. Grrr.

Even with a parralel system it would be hard to operate one as a true control for something like iron depletion, unless they were started at the same time and had all other parameters (bar the nails) the same. Might give a good indication though.

Wow.
Started reading this thread 2 days ago when references to RSG were starting to annoy me :-)
Only just finished now.
Really worth the read. I think I'm going to have to build one, however I like the idea Les? had of having it in the small white GB. I like my real GBs to be plants only.
A separate fully enclosed RSG would be great I reckon.

If you look at the expensive cannister filters, they use baskets to hold the media.
I was wondering if you could have a large multistage RSG, where you could open it up and easily add nails, calcium or carbon to each section when they begin to deplete, and just have a very slow flow through it...

Is there any particular reason people have been building them into gravel beds (excepting convenience)?

Nitrate levels higher than desired or expected to be higher than desired - due to too high a density of fish (feeding) to nitrate stripping plants.

yes VB I get that. I meant where the RSG is installed in particular. Is there any reason to build them, in gravel beds or would an external cannister style filter be better? Or at least no different. (I really dislike digging in my GB already :-)

I guess it would work either way once matured. I guess one advantage of putting in the seperate container is that it would be easire to clean, add more of them, remove some etc. I'd not be inclined to use a cannister filter for the purpose - would be constantly getting clogged and you may also need to have the pressure/flow too high. One advantage of the design Janet has come up with is that any excess water simply flows over the top and into the GB (same could be done using a seperate container full of media with RSG's contained within). Can't bee too anal on this one buddy - KISS principle I feel.

yeah I agree, I just don't like extra stuff in my GB... I wouldn't use a real canister filter, just the idea... The flow would be MUCH too high from all reports, I mean they are meant to encourage aerobic bacteria, not anoxic

I was thinking I could build one as shown below.
large PVC pipe, 200mm or so.
Screw on end caps.
infeed, overflow and outfeed, just as you guys have with your GBs
fill it with sand.
Get a tuppaware or other container with screw lid.
Drill holes in it, 6mm seems standard :-)
Fill it with your RSG media, charcoal, shellgrit, nails etc...
bury it in the sand.

Hook it up to a low flow pipe and voila...

Any ideas?

Not too anal is it?

You'd never know if your RSG was getting any flow through it. It's likely to just crog up and all flow occur through the orange stuff (I'm assuming gravel or hydroton or something. IF you were going to do it this way I'd have the tupperware container fitting snugly in the pipe so flow had to go through it. That way you can tell if and how much flow it is getting.

nope orange = sand, green = special media like nails or carbon or shells etc

But yeah snugly mught work better, I'll have to see what pipe sizes fit nicely

Doing a couple of mods to mine to get a better flow and reduce fouling, hooking it up to the new smaller tank so you are just gonna have to wait (and hope it works )

Installing in to the GB was simply convenient and foolproof. I'm happy with the way mine worked, and will keep this in my bag of tricks for future excess nitrate problems.

I like your grow bed install method the best because no more piping needed. The ability, you stated of turning the fill pipe for RSG on and off is the KISS solution. Harvesting some fish? Adding some more fish? Need more nitrates for the plants? Need less Nitrates for the plants? Adjust the RSG good to go.
Seems to be the answer to many things we encounter, crop harvesting etc.

I just put a container of sand and carbon in the sump, under the inlet to the sump. Maybe didn't flow through very well, and I'm not sure if it had any effect, but we should definitely be able to design one that doesn't clog and can be added easily.

Having the RSG after the gravel beds makes the most sense to me, as the thing couldn't clog due to solids, just to biofilm buildup.

KP

You might want to put a vent to air if you build one to allow nitrogen to gass off. Carbon is required in the filter as food.

DD

Might want to put it just before the sump as extra small feed of water. Most dump water into sump to oxygenate and gassoff before pump to FT for more oxygenation.