Backyard Aquaponics
A place to discuss aquaponics

Well I just realized it can't use a proper heat exchanger since it breaks the no-metal-plumbing-in-aquaponic-water rule but I really don't see why pex tubing just sitting in the pond wouldn't be just as effective. The pond water really ought to suck the heat right out of the pex, I'd think? I mean if you can heat a concrete slab with pex, why not heat water? I'll have a thermostat in the water to run the circulator for the pond loop.

If I wasn't clear, I'm talking about hooking my pond into my home's heating system, not some mass of water inside my home.

No problem. They make stainless steal heat exchangers. They are a little more expensive though. I think I'd go with the exchanger. The pex would work but why not be more efficient if you can.

You might compare the price of 200 feet of pex to a stainless steel heat exchanger. Unless space is critical LOL it'll get 'er done.

Man I wish I had that much land.

Hey Tori, great work. This is an awesome build.

I saw this today:
http://www.instructables.com/id/Compost-Heating-System/?ALLSTEPS

I know you said you don't have a lot of compost but you don't need it. With all those chopped down trees you only need to hire a wood chipper and get some sawdust from a local sawmill.

Not sure if it's practical but if I had that much space I would love to give it a go.

Regards, Martin.

Finally something to show, sort of!

My greenhouse foundation is done, and it's been filled with sand. On top of that I'm going to be putting stone.

Before the foundation was filled, I put in earth-tubes - a series of pipes underground to use the ground to pre-heat intake air and hopefully reduce heating costs a bit. Thanks for the idea, Rairdog!

I ultimately decided on an octagonal, in-ground fish tank. It's 8 feet across and about 6.5' deep. The tank has been framed to keep the sand out while I pad and line the tank with EPDM pond liner. I figure it'll hold about 2333 gallons (8830 liters). The top of the water will be above grade, overflowing into the in-ground sump tanks.

I have built (well, framed) two sump tanks that will be plumbed together so they remain at the same level. They'll hold about 1675 gallons, total (6340 liters).

Not much else to see yet except a lot of sand! The pond liner material will show up in a few more days but I probably won't start the lining process until the greenhouse itself is done.

Thanks for the idea, Martin; I may try something like the compost heating in the future... I actually have a wood chipper PTO attachment for my tractor, so I might some day try it with wood chips. For now though I think I'm going to make a homemade heat exchanger, in some form. I'm thinking a 50 gallon bucket that I pump FT water through. Inside the bucket will be a coil of PEX attached to my home's multi-fuel heating system. That way I can heat it with whatever is convenient: Propane, oil, or wood.

Actually I wonder - how does the heat released from composting wood chips compare with the heat released by just burning the wood? If it's comparable or identical, it would make more sense for me to burn the wood in my wood boiler than it would to chip wood solely to make the compost heater.

I'll have to ponder it. Thanks again for the idea.

Looks great Tori! I'm anxious to see how effectiveness of the earth tubes. Gaining heat from them in Jan/Feb with a 5' frost depth might asking a lot but they should help you balance the highs and lows in summer and winter. How deep are the tubes?

If you are already set up for hydronic heat why not put pex under the whole floor assuming you have a wood boiler set up for the house and it can carry the additional load. Maintaining 60 to 75 year round in GH will make your plants and fish happy. The GB temps are going to determine the FT temp as huge a radiator.

I'll definitely measure the temperature of the air as it enters and exits the earth tubes to see if it'll make any difference. I figure if it makes any measurable difference whatsoever it'll eventually be worth it. They're about 5' down, inside the frost wall.

My home's propane system is over-sized enough to take on some additional load, but I don't think it'll be enough to heat the entire greenhouse. I'll use it just for the water. When heating with wood or oil I have a lot more heating capacity, but I'm not always home to throw wood in... I need to design it for the lowest capacity system that might be in-use at any given time. So I'm not running pex under the floor but instead have a separate propane heater for the greenhouse air. Hopefully keeping the air warm will help keep the water heating needs down to a reasonable level. We'll see!

Looking good Tori, was the Cat excavator just driving by or do you have earthmoving equipment?

Thanks Slowboat. I actually have a volvo excavator - it's off to the left outside of the picture - but a neighbor who's helping me has the cat and wanted to use his own (the controls are set up differently on mine).

So, you live in a tractor rich area... Getting your neighbors to help must be easy, they are probably looking for an excuse to use their toys!

Hi Tori,
Great job so far,this is just my thoughts,your fish tank, how where you planning to get the water and solids out ? May i say that you are at the perfect stage to add a bottom drain to this tank,this makes the removal of solids so easy,for more information google Culture Tank Design,the one to read is by M. Timmonds and J.Ebeling they go into detail on this subject in respect of aquaculture. After reading it you can make up your own mind..

I was planning on inducing a slight rotational flow in the tank to get the solids in the middle and using an SLO. I'm terrified of leaks and it seems a lot safer than a bottom drain. But I'll read that paper you mentioned and see if it changes my mind! Thanks!

I suppose I'll also have to figure out how to get the solids out of the sump into the grow beds... Maybe I'll use a bottom drain there. Better a leaky ST than a leaky FT!

I understand the fear of leaks,but I have used them a lot for my Koi ponds and am using them in my fish tanks here,no leaks to date.
If you didn't want to use this method a circular flow so as to drive all settelabe solids to the centre of the tank,then your slo position vertically at the centre will remove the solids and no holes in your tank.if you are using a circular sump again the same process,if any other shape and you can't direct your settelabe solids to the centre your slo needs a horizontal length across the bottom with slots in to pick up as much as it can,help here is to keep some fish in the sump as well,they help keep the solids moving across the bottom as they swim about,so helping them to find the slo.

I'm afraid and I hope someone can allay my concerns....

I lined my octagonal fish tank with EPDM rubber. As expected, I had these great big, unsightly folds of rubber at each corner. I spent day after frustrating day trying to get them folded back neatly, and then glued to the sides so that water wouldn't get behind them and make anaerobic zones. I also intend to keep the water rotating, and didn't want the flaps to add drag. In the end, I found that it simply wasn't going to work and came up with what I thought was a better idea.

I cut a 6.5' x ~22' piece of EPDM and put it inside the tank around the circumference and glued the seam and the top and bottom to the original rubber, to make nice, smooth sides of the tank. I also glued strips to cover the seams along the bottom and the vertical seam.

I filled the tank with water, added a couple dozen little fingerling goldfish (which are not nearly enough to cycle the system but I figured they could tell me if they were happy with the water and the tank before I added enough to cycle it). The beds are not ready, but I have a pond pump/filter going while I work on the rest of the system.

So the other day I cut the hole for the SLO and ran into a huge nightmare. There is water between the original liner and the inside liner. Clearly one of my seams has a hole, which is the whole reason why we use a single piece of rubber in the first place, right? Leaking isn't a problem here, because the outside liner is intact, but I'm panicking that this water in between the two layers is going to get anaerobic.

I have no idea what to do at this point and need some advice. Should I not worry about it? Should I pull out the inside pieces of rubber and just leave the flaps that probably also have water behind them (and therefore the same problem, right?)

Or worse, should I rip out my whole tank and build a new one out of fiberglass or something?

Any ideas at all? Help!

Thanks!