Passive Aeration

[John Link]

Is it feasible to run a 1/2 HP pump from the fish tank at the lowest point to the max head height of said pump--to flood and drain grow beds and then back down to the fish tank.  This is in an attempt to grow more fish by providing more dissolved oxygen through passive aeration.  Any feedback/input would be helpful, I am designing a system to be used in sub-Saharan Africa.  Resources like electricity are scarce so I need to maximize the high calorie fish raising potential without adding all the modern technologies.

[Jonathan Kadish NYC AA Chair]

Pumping air is less energy intensive than pumping water so I would think that increasing your head height would not net you much if any energy savings. You do have quite alot of sun there and I would think a solar system would give you some amount of redundancy as your grid will probably not be very reliable. Remember that it only takes as little as an hour for your fish to die.

What size system are you planning?

[Cory Cramer]

An air pump can run on 3 watts or less. I would use that for aeration. Then lower the head height of your water pump so you can run a lower HP pump that uses less electricity. If your electricity is really limited, I have also run flood and drain with an airlift pump, but it doesn't have a fast enough flow to run a bell siphon, you need a timed flood and drain. (And, my system was small, so if it is a big system you might need more than one airlift pump to flood the bed in a reasonable amount of time.) I didn't run a very long trial on my flood and drain before I switched to a hybrid system, but it did work.

[John Link]

Thank you so much that makes so much sense.  I guess I need to learn more about pumps. The design of the system needs as few working parts as possible especially those run off the grid.  I'm reading a bunch on air lift pumps as a solution, I am not too familiar with pumps so I posted before I let my thoughts develop enough.  Even with the use of an air pump it is still more efficient to have the fish tank at constant height.  So its back to the drawing board, we are trying to initially setup a 1400L, 15 tilapia, 2 grow bed system.  There are more than 10 youth at the center so any less doesn't seem worth while.  I think there are plenty of working models out there to get us started.  Then once we adapt our system to the environment we seek to develop and involve the community enough to start production on a large scale projects.  The end goal is to utilize an air lift pump in a 10ft deep fish tank (10000L) distribute that to pretty sure the math on that would be 40 grow beds/sump tanks.  But that is very far from where we are now so if you have any tip on designing a small expandable system I am alllll ears.

[John Link]

Have you seen Buoyancy Hydro Airlift videos I feel there are new technologies available but yea thanks for the post are you running a mixed design system all together??? That's ultimately what I would like to see on a household level EVERYWHERE lol

[Cory Cramer]

I don't claim to be an expert, the following is just what I've learned from doing my own research for building an inexpensive off-grid capable system. I've had good luck with the two port version of this pump http://www.theaquaponicstore.com/ActiveAqua-Air-Pump-with-4-Outlets... but you'll need a 4 port version for two beds. (I think this runs on about 6 watts, from memory, but you can google the specs to check.) You would use two ports for the two airlifts (one for each growbed), and the other two would be connected to airstones in the tank for aeration. I like the clear plastic flexible tubing for the airlift for my indoor systems, but you'll have to encase it (or run it through) some pvc so the sun doesn't shine on it and it doesn't clog with algae. The most durable tubing I tested last summer was an airhose line (which I believe is made of rubber, nylon, and plastic). I'm not a scientist, but I think it should be safe to use (I didn't lose any fish in the system). I ran a test with it all last summer and it worked great. You'll probably want your tubing about 3/8 inch thick, that's what I have had the most success with.

[Cory Cramer]

Yeah, I'm developing a mixed design for aquariums and possibly rail barrels, that people can just drop in and go. I'm on about my 5th design, and getting close to having the kinks worked out.

[Cory Cramer]

I should add that I've really been focusing on indoor systems even though I did run some tests outdoors last year. I live in Iowa and my goal is to be able to grow year-round in the basement, so that has been my main focus.

[John Link]

Thanks dude where would I incorporate these aerators on a CHOP type system?  Mixed designs the way to go its pure "business" the fish should be the main concern they provide the most amount of food for the least amount of money ie fish feed.  
Cory Cramer said:

I should add that I've really been focusing on indoor systems even though I did run some tests outdoors last year. I live in Iowa and my goal is to be able to grow year-round in the basement, so that has been my main focus.

[Cory Cramer]

You could put one airstone in the fish tank and one in the sump, but the airlift would be trickier with a sump. I would be more inclined to just go straight from the fish tank to the grow beds, but instead of using one airpump with 4 ports, use two airpumps with 2 ports each (using the same amount of electricity). Then what you could do is, with two simple timers, run one airstone and airpump for 1/2 hour to one growbed, then run the other pump for the next half hour to the other growbed. Your fish tank water would only fluctuate a little bit, you would always have one airstone running in the tank, and you could run the whole system off about 3-4 watts an hour.

With the CHOP system you would have to add a lot of stuff, on a bigger system it might be worth it, but I think for this size you could get by using a lot less electricity, if that is a priority, sticking with the single pump, single tank design.

[TCLynx]

Keep in mind that airlifts are restricted in the amount of height they can lift the water and they need an air pump that can push the air down to the required depth under water.  Most of those little 3-6 watt air pumps are not going to push air down into a 10 foot deep fish tank since it takes 1 psi to push water down each 28 inches.

[Cory Cramer]

That's right, TC. You really have to design the systems around the pumps, but 1400L is what, about 300-350 gallons. That's probably only 2ft deep. If the grow bed is 12inches deep, he should only need to raise the water 18 inches or so to get it up to the growbed. My system only had an 8 inch grow bed so I didn't have to lift my water quite that high, but it could have lifted higher and my tank was only 18 inches deep. I really like the airpumps here at the AQ store, too, especially because the ports are made out of metal instead of plastic (which tend to break) and they are adjustable, and more powerful than the cheap ones they sell at walmart.

One other key with using airlifts with a flood and drain is that you must have a spray bar. They don't move a whole lot of water and it is important to get the nutrients spread out somewhat evenly over the whole system (which is probably true with any system, but especially true when you have a low flow system).