Backyard Aquaponics
A place to discuss aquaponics

Hi Everyone:

I'm trying to put together a constant height system using pond liner and constructed grow bed. I have a couple questions (maybe this is the right place, maybe it's not) that I'm having trouble figuring out.

My fish tank is going to be 5' x 5' by 4' deep giving me about 750 gallons to work with. My sump is going to be 4' x 3' by 4' accommodating about 360 gallons. The grow bed is going to be 20' x 5' and I'm going to make the gravel 13" deep so I can draw the water to a full 12". This should net me around (based on a figure from this site - thank you) 300 gallons of water when that system is full. Ideally, should the pump fail, the fish tank will do as designed and overflow into the sump and everything will stand until I can fix it, with no loss of water. What I am having trouble figuring out is whether or not my 1200 gph koi pond pump will be sufficient, how much air I need (some of those air pumps get pricey fast), and whether or not I've calculated my grow area correctly. Based on what I think I've learned, I should be able to handle 100 lbs of fish and 100 square feet of growing area.

I'm also concerned about the weight of the grow bed. Based on what i've been able to gather from the Internet, when this thing is flooded and full of gravel I should be looking at a frightful 5 or 6 tons. I'm not even sure how to engineer that so it doesn't sink and/or burst apart. I'm on a budget so working this out with the least expensive materials is the best (if I weren't broke I'd just order the 1500 dollar tubs and be done with it instead of digging a hole).

I know many of you are going to try to dissuade me from going with such a large system for my first run but, I'm confident that this will work out well and I've read that the minimum system for stability is 250 gallons. Going above that, and considering I already have a pump, I'm working within what I have. The materials for a smaller system would be close to the same due to liner manufacturing dimensions. I'm not willing to give up the sump system as that's a feature I want to show off, that you can have a full pond, and it'll look good.

I hope to be a valuable resource to this community and I'm looking forward to everything I can learn (well, not everything, I don't really want to experience fish sickness or plant problems but I'm ready)!

Yay for whole, local, unpoisoned, unmodified food!!

Hi Paul and welcome to the forum, sounds like you have done some homework already. I can't do a quick conversion at the moment, due to cooking the family dinner, hopefully someone else can chime in and help out before I get back. Did you know we lurve pictures?

The pump should be sufficient depending on head (height difference from the water level in your sump and where you will be pumping to).

Don't want to talk you out of a large system, but one large growbed of 20' x 5' (or 6m x 1.5m) could be a problem in terms of weight and required support (as you have already mentioned). Is it possible to split it into 2 or even 4 beds?

Hi Faye:

Thanks for the welcome. Hope dinner goes/went well!! I was doing my own as well. I had butternut squash for dinner-ish. Yeah I'm a nightowl American or I'm just on a different hemisphere's schedule [shrug].

The only images I have at the moment are my wonky sketches to keep the stuff square in my head. I'm not even sure, if I were to wait a year, I'd be able to decipher them myself. I do plan to document the whole thing as soon as I start and I should have some carpentry help here this week for engineering the weight issues. Hopefully they really know what they're doing.



Hi arbe:

It's possible to split it, but doing so doubles the complexity of plumbing, and requires the engineering and building of an additional bed and support system. I'm aiming to simplify all that by simply having a massive grow bed. I'm sure there are going to be problems as of yet undiscovered with it, but I'm hoping the nature of the flood/drain system will mitigate most, if not all, of the problems relative to water/air delivery. Even if I did split the load, I'd still have around three tons per bed to deal with. That means twice the cement footings, (if that's the solution), twice the bracing, and twice the ends. Doing that would also double the possible leak sites.

Leveling will likely be an issue as well but I figure if I build in a means of handling that, (hopefully with the help of my engineering type friends) I'll have that resolved before I scoop my first shovel of dirt, or make my first cut of wood.

An additional reason I'm aiming for this size of bed is that it is also the size that is listed as an optimal bed size for raised bed growing in the book, "How to Grow More Vegetables, and Fruit than You Ever Thought Possible." I'm kind of hybridizing a system for myself, my budget, and my environment.

Really it all depends on what my friends and/or what people here say. I'm still at the point changes are easy to make and I'm willing to hear opinions, particularly when they're supported by experience.

arbe: I'm guessing around ten feet of straight up pipe (four from the bottom of the sump, three or four to the bottom of the grow bed, and another 1 or 2 feet for the gravel and spillway). According to this site: http://www.saltycritter.com/pumps/mag-drive.htm my head height will be between 600 and 650 GPH. Don't I need to have enough to move the entire system at least once an hour?

I also don't know how much aeration I need and I haven't been able to find a good source for that information. Everything I see says more is better but when I look at air pumps I quickly determine that more is more expensive.

600 - 650 GPH is pretty close to the volume of your fish tank and should be sufficient. If you are concerned get a larger pump.

I have a 5000L fisk tank (approx 1320 US Gal) with a 4500LPH (approx 1200 US GPH) pump at 0 head. I have about 0.8M of head so according to the graph on my pump it should be pumping about 3800LPH (approx 1000 US GPH).

I had no problems with water quality etc with my system.

I think I'm going to rework the system I had in mind. I had a friend over who said that I'd be retarded if I were to put 5 tons of rock and water completely over an in ground pond that I will have to work on. He didn't like the idea of possible death.

I really want an in ground, constant height pond but it's looking less and less practical. Particularly in the context that I want to get a system up and running so I can get some food out of it sooner than later (without going broke).

I have watched a LOT of the videos you've all posted. Thank you for such a selfless contribution to the world. I have a few questions though. I've rethunk my original thought and I'm going to start with an IBC system. Depending on volume it isn't working out to be cheaper than a liner system but the person interested in helping is paying for the IBC's so, at least in that context, it's cheaper than any other option I have.

With that in mind, I'm toying with a few ideas. My primary crop focus is going to be basil. I have read that it is in the mint family and that mint absolutely loves aquaponics. I have also read that I should probably NOT use media when growing mint. This makes sense but it also creates a necessity for filtration.

I'm also going to be working with four IBC's and I'm not sure whether I want to plumb them together (reducing the number of pumps) or if I want to have independent systems.

Also, if there are... I'm guessing here... around 250 gallons of water in an IBC when chopped up, I would have about 36 pounds of fish I could grow, and about 36 square feet of growing space (I'm not really good with metric yet but I'll get better as I continue this). Aren't we wasting a good deal of growing area by only using the lid of the IBC? Aren't they only about 4 feet by 4 feet?

Also: I watched one of the videos (the half hour one) where there is a water distribution system for the grow bed. I'm curious to know how that doesn't get clogged regularly. Wouldn't water find all the space it can without the additional plumbing? I was also not totally clear on which type of system that was. It looks to be a constant flood system (with the standpipe instead of an autosiphon).

Based on what I've been reading and what I want to grow, I think I'm likely to do a raft system with the floating foam rafts and the net pots (unless someone suggests otherwise for basil).

One last thing... for now anyway... how many bags of the pellets does it take to fill the grow bed to the depth in that video?

The reasons for arranging the irrigation grid are to evenly distribute water around the bed whilst keeping it out of direct sunlight. You may have seen some systems where the water pools in at one point and dumps solids from the fish tank on the surface and algae grows. The water does find its own level, but the grid around the edge is easy to get to for maintenance if the roots find their way in, which may happen after an extended period of time, 4-6 months, maybe even longer. There are holes drilled under the grid and the water trickles easily out from there. Also doesn't waste much planting space.
You are correct that we use a standpipe, (very simple to set up and manage with no technical tweaking required) and it is running continuously, because the aim was to make it as simple as possibly and use minimum components. You could easily include a timer and run it 15 on 45 minutes off, the choices are endless. We have seen a rush on IBC systems since we put up the Youtube video and IBC manual because it makes it a cheap way for people to have a go and see for themselves that it works. This includes people that have wanted to do aquaponics for years and couldn't afford to buy a complete system or justify the cost.
The growbed contains 4 @ 50 litre bags of expanded clay. Hope this helps Paul.

I wish there were a +like button on this forum.

Thanks for the speedy response.

Would the clay be better than a raft system for what I want to grow?

if you do a raft system, you'll have to make some kind of filtration unit, it can be diy, but bits of plumbing add up, as does the material used in the filter..some folks have been painting their foam rafts as well to extend the life, but another cost added..
gravel growbeds work great for the filtration as long as you don't overstock.. i've taken quite a few basil cuttings from our outdoor plants (lime basil, lemon, thai and sweet) and just stuck them in my gb's (half gravel half hydroton) and the cuttings did great!
whatever you do, your system will evolve, or you'll be working on an upgrade before you know it