Backyard Aquaponics
A place to discuss aquaponics

Been thinking about aeration and things, we all know how good it looks when your siphon boots up and swirls the tank/sump with lots of air... i miss this and it worrys me now not using siphons and putting shower style heads on the ends of the tank inlet just restricts flow so thinking got me into setting up a Header tank ontop of my FT then divert some flow from one pump upto it, install a Bell Siphon into it with a predrilled endcap in a shower style too inject a nice shower into the tank with plenty of pressure. The addition of some plants in netpots in a raft style arrangement may be a good idea to make the addition also viable on a growth sence.

Also been thinking about placing my Aerators in the Shadehouse so the air they draw is from a location that has an abundance of oxygen (as plants create it) not sure if it would have a large impact or not but im sure if it was a large compressor style that draws a lot of air it may have some impact....

Just a few ideas..... pondering out loud if you will

Pondering aeration... I tend to think many people put a little too much emphasis on aeration when chances are your water will be saturated with dissolved oxygen all along just with pumping, without any of the added aeration measures.. The unknown can be scary, and not knowing what your DO level is, leads many people to think that perhaps it might be low, or if something happens to the fish and they don't know what caused it, then perhaps it's low DO levels.

I've never had a problem with low oxygen levels in a system except when the power has failed.. I find it a little strange when people are turning their fish tanks into spa baths with huge air pumps, when really they are not required unless you have extremely high stocking levels/hot water etc.. With such extreme aeration It means that you can't see your fish, and I'd rather see my fish at a glance to see their behaviour and their bodies, as these are your best means of knowing when there is a problem..

I don't think the aerator in the greenhouse would make a lot of difference as it's not so much the oxygen level in the bubbles, but more the water movement that the rising bubbles create that allows oxygen to be absorbed at the water surface.

Still not that I mean to try and talk you out of fiddling, it's always fun to fiddle, change things and add more.

You will get more from your money by using your air pumps rather than lifting water to a header tank. However, if it is the aesthetic of having thr suphon dump every now and then then go ahead.

As for placing the autonomous near the plants even if it did have an effect you would need to move them at night. The more effective it was during the day the more important it would be to move them at night.

Ahh its good to get some other prospective on the ideas... best thing about this forum... plenty of minds that think alike and very differently, other that have had experience in many areas and, plenty of tinkering knowledge....

Love it!!!!

Ill definitely agree with the spa bath effect EB! When I first had my silly stocking levels of trout I invested in a massive air pump to get me through till I had something sorted. The thing is now it throws so much air out it disturbs the water so much I can hardly see the fish!! I have to turn it off every morning so I can check they are ok.

And it sort of takes away half the fun of AP when you can't see your fish...

Lots of stuff from EB that I agree with deleted.



This keeps on getting repeated but it is not true. Gas transfer occurs at the boundary of water and air. Whether that is the completely still waters of a mill pond, the ruffled surface of a fast flowing stream, a droplet of water flying through the air or a bubble of air traveling through water does not matter. In well mixed tanks (most AP FTs) the key to achieving good aeration is to increase the m2 of water/air boundary. The most energy efficient way to do this is to throw watet into the air using a paddle wheel. Since this is generally not practical in AP the next best method is to inject air into the water. It is more energy efficient (to a point) to do this at higher pressures with an apropriate air stone so that:
1. the surface area of the air water boundary is maximised;
2. The bouyancy of the bubbles is reduced so that the time it takes for them to reach the surface is increased allowing more time for gas transfer to occur.

If too high a pressure is used the small bubles tend to coalesce which defeats the advantage of using a higher pressure and wastes energy. Also higher pressures in deeper tanks can lead to toxic levels of nitrogen.

To get around this second problem if more oxygen is needed than can be supplied by atmospheric air alone then you use air with a higher concentration of oxygen. When tuning such systems the design aim is to have all the oxygen in the bubles that can be absorbed into water to have done so before the bubble gets to the water surface. Any oxygen above water saturation levels is then lost into the atmosphere and the energy used to concentrate and deliver it wasted.

In water bodies that are not well mixed a secondary effect (eg AQ ponds) is very important which is based on the rate at which gas is transfered. The rate at which the transfer occurs depends on the difference in partial gas pressures or concentrations of gasses in the air versus the water. In poorly mixed water the current produced by aerators moves oxygen poor bottom water to the surface so that the transfer of oxygen into the water is maximised because the gradient of oxygen concentrations is maximised. If this current is produced by air bubblers then oxygen transfer still occurs between the bubble and the surrounding water. In fact in really poorly mixed waters the importance of the current bringing oxygen poor water to the surface is critical because all the available oxygen has been stripped from the bubbles before they reach the surface. In most AP systems because they are well mixed by the relatively high turn over rates [O2] are uniform so the bringing of bottom water to the surface doesn't make much if any difference.

I think you would actually get more flow by diverting the water to the fishtank. Pumping uphill kills the flow. I'm just learning about pumps now.

for visual interest, try a wall fountain. ie water running over some glass or something can work really well, or a deer scarer if you miss the irregular water flow.

Fun, yes but fidling can be counter productive as I can atest. Not asking questions can also be counter productive, as can not taking advice, Um I I think I just confused myself.

That's what I had always figured originally Stuart, but there's been a constant flow of people on here saying that most of the transfer of oxygen happens at the surface of the water and it's more about the water movement than the bubbles...

From what I can see you would probably have more surface area with all of the bubbles rising from a couple of air stones, than the whole surface of the tank... I dunno, I know that our system here never really have a problem with DO levels, so I'll remain happy in my ignorance..

As far as efficiency of air pumps Vs water pumps for oxygenation, well that was a very hotly debated topic a while back..

Yeah I think it comes from people reading about pond AQ which has a lot of stuff freely available on line.

I was rather involved in that debate with I think Frank. Now that I know more I can repeat that lifting water is expensive when comparded to sinking air.

What debate? Oh that debate...

My thoughts are a system that is well aireated [ not so much high oxygen content but a system with a lot of air stones ]i am presentley running 12 at least 2 in every fishtank and sump
Is very forgiving
i have one bed that is very blocked with mud [ i bet theres anerobic zones in there ]
The ex duckweed tank with the silvers has about 3 in of sludge shells rocks [little kids are shits ] and 2 water lillys in pots
in the system i have trout [we all know they like pristine water ] silvers jade perch and goldfish

I use a powerhead in my FT. its more like an outboard than a pump. It cant raise water at all but shifts 5000lph for 12 watts. My 1.2 meter *2 surface area must be changing over in a fraction of a second. And the fish spend most of their time right in the strong flow so seem to love it. (silvers)

I'd love to see a test.

I wonder who has a DO meter that they really need to dust off soon to test the BYAP trials and satisfy all the questions

I'll have one real soon.