Backyard Aquaponics
A place to discuss aquaponics

“Self-aerating grow beds?!!! Yes, thats what I am hoping for, but lets start more simply.
Most systems use sump tanks; main advantage is the h2o level in the ft doesnt change, as the gbs flood and drain. The level in the sump tank rises and falls, instead. Hold onto that thought.
Many use totes for their sump tanks, and a tote bladder is not only water tight, but if uncut, potentially air tite, as well.
So, if all the connections transferring water to and from the tote are air tite, we have a potential compressor.
So, I plan to have my gbs dump into an upright vertical pipe, going down thru the cap of the 6” opening in the top of the tote, said pipe extending down into the tote to well below the low water mark, and with an airtite seal where the pipe goes thru the lid.
Water will be pumped from the tote via the 2” opening, which should also be well below the low water mark.
And, this will not work, if these connections are air tite. As the pumps start pumping, at a certain point, either water will stop flowing, or the bladder will collapse, cause air needs to come in, to fill the space where the water was.
So to address this, I will drill a 1” dia hole, down thru the top of the tote, 5”-6” out from the center opening.Then get some thin, stiff but flexible plastic, like (here, at least) a drivers licence, or like a standard “playing card”. Cut a 2” square, and glue it, 3 sides only, to the inside surface of the tote, so it covers completely the 1” hole.This is a simple one way valve; water level drops creates vacuum, which pulls the plastic away from the tote enough to allow air to get sucked in.
However, water rising tries to displace the air in top of tank, increased pressure pushes plastic firmly against surface of tote, making a seal.
Which means trying to put water into the tote does not work, but easy to fix; put another 1 way valve in the top of the tank, but this time with the flexible plastic on the outside of the tote; this one will allow air out, but not in. And it is this one which will be plumbed; I will have to get a pipe flange (what you would use to use pipe as table leg) and get one big enough that that I can attach it over the 1 way valve so that it would not interfere with its operation, but would funnel this compressed air into the piping i would attach to the flange. I will then run the piping to the ft. I know, I said self-aerating GROW BEDS, patience.
Everything about dissolved ox says there is no advantage in putting your bubbler deep, but there is a disadvantage; deeper it is, the more air pressure it takes to make bubbles.So, bubblers just below the surface, as I suspect this compressor is going to be low pressure.
Also, there is a way to increase the volume of compressed air produced, IF the system can be designed so the gbs dump into a vertical pipe that remains vertical into the sump. Drill small ( 1/16th”) holes around this vertical pipe, angled downward. As the water goes down the pipe, it forms a venturi, which draws air in thru these holes, and the bubbles are carried with the water.
So, you dump 1 cubic ft. of water into the sump tank. Without the holes, you would compress 1 cu. ft. of air. With the holes, you may get 1 ½ cu. ft. of air.
Its an an ancient way of compressing air called “trompe” , and you can google to learn more.

Now that we have the concept, its easier to describe same idea, applied to grow beds. Visualise a typical grow bed, in cross section. Got your floor, and 2 opposing walls. Imagine these walls are a “double wall”, at the top turning 90 degrees, for 1 ½” - 2”, then 90 degrees again, and down into the gb.Could go all the way to the floor, and have holes too small for the media, down along the bottom, or be crenelated, or even stop just short of the bottom, so there is a slot all around. Key point is the water can go in, as soon as the gb starts to fill, but the media stays out of this chamber created by the double wall. Put the 2 1way valves, and plumb to bubblers in the grow bed, and “bobs ur uncle”.
For k.i.s.s., that's it. However, this would waste some of the compressed air.

As tbe gb begins to fill, once the water level is above the top of the openings in the bottom of the inner wall, water rising in this chamber betwèen the inner and outer wall would compress the trapped air, and it would go out the bubblers which would not be submerged yet. It would complicate, but COULD put a float operated valve on the discharge line (going to the bubblers) with the float inside a media guard, in the grow bed.
That way, as the bed begins filling, so will the chamber. But, with this valve closed, and the trapped air unable to go, the water level in the chamber will stop rising, even as the level in the gb continues to rise, until it raises the float, allowing the air to go to the bubblers.The h2o in the gb may even drop slightly, as the 2 levels equalise. Its also possible that this inner wall could be on an angle, getting farther away from the outer wall as it goes down. This would minimise the amount the double wall would reduce the surface of the grow bed, while increasing the amount of compressed air from each cycle.
Until I build, I will not know if this will only be supplementary air, or whether, especially for the fish, it can be my primary source. Even so, easy to see scenarios where the gbs would not be f and d ing, (power outage, plumbing repair, etc.) so would still need a battery operated back up air source.Jim

KISS is right. KISS APPLIES... the GB fills and drains, fills and drains.. forcing air out and sucking it back in..

How much simpler is that..
..
.Peter

Just thinking.. putting these aeration devices in GBs will take up valuable space and then add little extra benefit..

TL:DR please?

This should be interesting but I'm going to need some pics I think . Venturi's are fairly common here but haven't seen too many sealed tanks.

Sorry, I AM new here. I was under the impression that fish tanks need some additional aeration, by bubbles or sprinklers on the surface; that the f'ing and d'ing of the gbs isn't enough.
Thats why (I thought) people talk of having battery powered air pumps, for power outages, to keep the fish alive.
I also thought I read on this forum that some reccomend getting additional dissolvdd oxygen to the plants and N.B. in the grow beds.
Please clarify where I got it wrong.
Also, this is a proposed build, no pictures yet. Did I post in the wrong place?
Thanks, Jim

You didn't get it wrong Jim. Fact is that sometimes they do and sometimes they don't. System design is important, the type of fish, and the number as well as the size of the fish, also the water's temperature which helps determine how much oxygen it can hold.

If you design in a lot of splashing and you have fairly light fish loads and aren't running trout in warm water, you're probably good to go. With Tilapia you may get by with larger fish loads and less splashing since they're well adapted for low oxygen levels. Because water holds more oxygen at lower temps you can get away with adding less in the Winter as well. Just moving water around can often be enough but sometimes you need more.

FYI other gasses in the water also affect the oxygen holding capacity of the water.

TS:DR

Hell I have abbreviations..

I have no idea what the abreviations mean?
Picking up from my intro: wife and I moved out from the city in July. Living in a trailer in av rv park, and shopping for a,piece of land.Plan on going off grid, moving onto the property, solar for electric, propane for refrigerating food, evaporation for climàte control, hauling water, (maybe well eventually) humanmanure composting, and aquaponics to grow much of our own food.

Don't see a need for high stocking densities; we LOVE to eat fish, but not every night. Until we pick our piece of land, won't know the exact climate, but will probably be around 3000' elevation.
Summers with highs of around 105F, and winter lows which rarely get to freezing, and don't stay for long.
So, I'm thinking Talipai, although if the winters enabled us to grow some trout, that would be great!
Basically, 2 seasons here, very subtle "spring" or "fall". Its either coats or t-shirts.Say 5 mos. of 1, 5 mos. of the other, with a 1 month transition..
As you say, it all depends on the system, and the location.Still designing the system at this point.
Our overall goal with our aq system is our goal with all of what we're doing; to lower our "cost of living" as much as possible.
So, with aq to produce as much of our own food as is practical, and be getting healthier food, as well.Not looking to go commercial or anything.Maybe sell our excess produce, but thats not a major goal or focus, althougb this area IS a "food desert"; if you want fresh produce, you can order a salad at one of the 4 restaurants, or get "fresh" apples or bananas at the convenience store.Other than that, its a 60 mile drive to "town".
No fire dept. or ambulance. No LEO, either, unless you can wait an hour for deputy to drive out from town.No town gov't. actually.
First priority is to finish my solar system, so we will be able to move onto our property, once we aquire it.Still, I can begin designing my aq system, aquiring materials for it, now. And, might start a small system, to test things out, and start lowering our food costs and improving nutrition even as we move forward.
My system will have a greenhouse, or grow room, so some ability to moderate the extreme temps for plants and fish.
Jim

A couple of things -

Tilapia will handle lows down to around 50 to 55F but die below this (some might before you get there). You'll probably have to heat the water some in the winter.

You may need to look into evaporative cooling for the high end of your temperature range unless the greenhouse is well ventilated.

Tilapia will give you better fish production than pretty much anything else and they are durable as long as you can keep the temp up for them. The greenhouse should help as long as the beds are inside as well. If they aren't then you'll need to cut them off for the winter since they act like heat exchangers.

Yes, I gathered from my reading tilapia are prolific, the rabbits of the fish world. The fish tanks will be under the greenhouse, and can be insulated. We moved here June, so know what the summers are like, still seeing how cold it gets in winter.

Am planning on some cooling for the greenhouse in summer, hopefully the sun will be sufficient to keep it warm enough in winter, prepared to add some water as thermal mass, so should be o.k. Will just have to see if I can set up the system to go tilapia year round.

The greenhouse is a "cargo box" like you see on delivery trucks. Similar to the box on moving trucks. Its a "curtain side"; one side is open, to make loading with a forklift easier. It is 8' wide, 20' long, and 11' high, and has the standard roll up door in back.

I'm thinking to set the 4 corners on totes, filled with water and on a firm foundation, to support it. Close off the open side with twinwall, and face it south, hence the greenhouse.May also put twinwall
On the south 1/2 of the roof, if needed to give the plants more light.
Thinking the sump underneath this, and the fishtanks 1/2 underneath, with part projecting out from under on the north side, for access to the fish.
Inside, on the north wall, water storage for thermal mass. I have provisions for ventilation and cooling, in summer. Hoping I can rely on the sun and thermal mass in winter, but we'll see. Jim