Backyard Aquaponics
A place to discuss aquaponics

Just as long as were getting o2 back in our tanks!

from reading all this, am i right to think that smaller bubbles in deeper water are best?

IMHO yes

Finer air stone at bottom of tank

my tank is 3 1/2 feet deep, i have tried to put the airstone at the bottom of the tank, but my pump is not powerfull enough, so it is about halfway at the bottom. does anyone recomend a pump that will work in deep water that is not $300? i am useing a walmart pump now.

what height is yr return water?

about 5 inches above the top water level

MC, the water in my tank is about 4' deep. I use an Elite 802 air pump
http://www.theaquariumshop.com.au/shope ... r+Pump+802
From memory I paid about $20 (I got ripped off )
This pump runs 2 10cm diameter discs to the bottom of the tank.

Oh yeah, the pump is hanging about another 2 foot above the top of the tank.

I'll chime in here. I did a bit of research in college about thermal stratification in lakes and ponds. The information I read then (at least 15 years ago) stated that air bubblers would help diffuse oxygen into the lake or pond -- but that the agitation of the water -- basically the pumping action of the bubbles lifting a collumn of water from the bottom to the surface -- was of more benefit than the actual bubbles themselves. In fact, most of the pond aerators I have seen use propellers or paddle wheels to bring oxygen deprived water up to the surface. I have seen designs that use inverted "U" tubes or counterflow to inject air bubbles into water under pressure -- if both the air and the water are under pressure, more oxygen can be "forced" into the water -- possibly even to the point of supersaturation. And from what I remember, water that is supersaturated with air can give fish "the bends" from excessive nitrogen.

I've also read that a jet of water spraying into a body of water is an efficient method of aeration.

It is somewhat hard to separate causes and effects when there are multiple things going on at the same time.

I say -- use what works for you -- even if the experts advise otherwise.

found one for $13 here,
http://www.aquaticeco.com/index.cfm/fus ... 3/cid/3910
for a few bucks more it looks like i can get more cfm?

1 thing to consider in aeration also is doing it in the most efficient way (energy wise). By creating a good waterfall effect with water returning from grow-beds and adding air through f&d cycling is an efficient way to add O2 because this process needs to happen as part of AP anyway.

I am not against bublers, but the only reason I have one running in my system is because I have my pumps off at night at present. Also, it provides comfort in case my pump (single pump system) failed. My backup, power failure, method of aeration actually uses a water pump, not an air pump.

Sounds good.

I hope no one took this thread the wrong way. I wanted to encourage discussion, hell, i'm first to say i was wrong if some once can logically show me!

I too think that there are more "free" ways to gas exchange. Its a sweat deal that the F&D of the beds does provide this.

I read an article posted by the (I believe) the Mississippi or Tennessee Ag Extension service that discussed the merits of different surface agitation systems to increase DO in aquaculture ponds. The main recommendation that they made was to use a paddle wheel as the main method, and that many other methods were either ineffective or merely partially effective. Since they were looking at aerating larger volumes of water (ponds with say a surface area of one or more acres and depths of around 4 feet) they did not mention the effectiveness of using using submerged bubblers connected to air pumps. They did say that the use of pond "fountains" did raise the DO slightly, but was of a greater benefit to lowering the temp of the water when the water was pumped from the bottom of the pond. (Naturally it would be, the water at the bottom is usually cooler than that at the surface! Duh!) In a tank system, like most AP systems use, the bubbler will add DO, but it is unclear to me as to which will provide the greater amount; agitation or bubbling.

Kevin

The best way would be to move the water solely by powerful airlifts.. then the question of bubbles vs agitation becomes academic

The great DO debate, if you look at aquaculture, most of the fish farms I've looked into use paddle wheels for aeration. The next big group use pure oxygen through a series of degassing towers and oxygen contractors to supersaturate the water.

One partcular farm used the water pumps to aerate the water, but kept paddlewheels onsite for emergency use because they could run them with generators. After Katrina, they were without power for MONTHS and only lost the stock in one tank that was actually damaged by the storm.

Diffusers are more effective in 'deep' water, and by the aquaculture definition, deep is 10 - 20 feet deep. And that's using fine bubbles.

From what I've been able to find online, airlifts are becomming the most common way for fish farms to move water through the system. And an airlift can be an even more effective system as each airlift does a combination of moving the water and aeration.

I keep going back and forth on how I want to set up my system. My current plan is to do a combination. Using a regenerative blower for both water movement and aeration. I like bubble diffusers, especially through bio media. But I'm still thinking about using a standard submersible pump to move water through the aquaponics side of the system.