Pond Boss Forums AERATION Systems questions question for aeration experts....Cecil?

Hi, One of the new fingerlings trying not to get eaten alive. Brief background, 1/2+ ac. pond 23' ctr. depth, 2/1 side slopes, spring fed. 350-400 trout+fatheads. Ok... last summer was dry my springs couldn't keep up with evaporation rate. To resolve I'm building system around a Gast 741R 1/4 h.p. compressor. Can anyone suggest hose (weighed vs. non-weighed) and diffusers? Also, check valve placement and pressure gage. Any suggestions appreciated. Thanks Slydog

Hi Slydog -
According to my calculations, your compressor won't be able to push air much deeper than around 15' (requiring 8.7PSI) I also recomend membrane diffusers as they will put less back pressure on your compressor. Weighted hose definately 'out weighs' the un-weighted as far as ease of installation and less hassle with sections of unweighted hose floating to the surface.

Anyone interested in a low-back pressure diffuser should check out Mix Air Tech diffusers. Cary Martin sells them as well as Keystone Hatcheries. The material is designed for wastewater treatment plants where they are concerned with low back pressure from their blower systems. when placed against other diffusers on the same compressor, the Mix Air will rob most of the air from the other diffuser. We did the tests in our trout ponds against the tube style and the membrane discs. Had to turn the air way down on the Mix Air's to equalize flow.

Slydog,

Trout? Are you sure you want to mix the water column? If so I would only do so at night.

Aeration will increase the temperature durring the warmer months of the year. You will need to moniter the temperature closely and as Cecil suggested, aerate only at night durring the summer and place the diffuser in shallower water to allow a deeper cooler refuge for the cold water fish.

RBurke is right about the reduction in back pressure with these new membrane diffusers. Sue is correct on the pressure requirement on reaching the deeper depths of your pond. You will not be happy with the performance of your 1/4hp if you desire to go that deep.

Like Sue mentioned, to reduce the chance of warming your pond too much to hold trout, you may want to place the diffuser in a more shallow location. If you keep it at the 10 foot level, you can use your 1/4hp. Are you at any elevation?

Generally, trout require water colder than 68. Another option to help keep it cool but aerated is to as mentioned aerate at night but add a surface aerator along with the bottom system. This surface aerator will act as a cooling tower at night when the water is thrown into the air. The bottom diffuser will eventually bring it to the lower levels of the pond.

Lastly, without a doubt, use self-weighted tubing. Save yourself the headaches and problems associated with non-weighted tubing.

Sly, Looks like you are getting a lot of the bases covered, Let me just add a few key points as some might be overlooked. If this pump (and I believe you have stated it is) a Gast 741"R"rocking piston pump and is a 100 psi model with a cfm of only 1.5 it changes things somewhat.A check valve should be built in the unit (pump)already as a back flow does not happen with pistons. The Mix Air type diffusers do not need an external check valve but should have one with low pressure (10 psi) rotary vanes. The Vertex CoActive Airstations have them built in the bladder surface and when the surface slots close the water pressure presses the rubber bladder down on a seat when the power is off so either unit will work. As far as back pressure between a MixAir type and a Bladder type(Vertex) diffuser it will have no effect on this model of pump.( not enough to calculate)You still have to overcome the water pressure regardless.I would be more concerned about the ability to exhaust off (regulate) from any type diffuser to slow down the circulation and perhaps most important monitor your water temps.I agree that putting any type of diffuser in a shallower area will be better but in your size pond if your spring is not adding 40-75 gpm of 55-60F water any type of diffuser placed at any depth running 24/7 will probably warm the water column too much for 350-400 trout.As far as a pressure guage it will tell you when your intake filter needs cleaned and when and if your diffuser is plugging ( that wont happen with the two brands mentioned)or if the line has been pinched so "yes" on the guage.Weighted hose "YEP" Its the ole saying "do it right do it once" You may be able to size down to 3/8 weighted tubing depending on the diffuser you use and the total length needed to save some $$ You may also want to consider adding a summer diffuser that has a riser that puts the diffuser approx 3-4 ft under the water surface to surface circulate.( both produts mentioned can be built that way) It would have the effect of a seperate surface aerator without the cost and would only require a manifold to switch away from the main bottom diffuser, this unit would be run when bottom temps were becoming too high.Hope this helps. Ted

Wow,

Thanks guys/gal for the world of info on this. Ted, you are correct. The pump purchased is a Gast Rocking piston pump 100 psi/1.5 cfm. Company that sold me this unit.... plus other ads on pump insured that it would be adequate for aerating 1/2ac. pond and would pump air to 20+ ft. Was I misled? Concur with evaluation of others also about temp. concern. Was only considering nighttime usage in midsummer period. Was looking at Vertex Airstations, Would you suggest twin disc or would one disc be enough? Thanks again.... slydog

slydog, your 100 psi unit will produce air easily to 50ft deep. Since you only have 1.5 cfm (1.3-1.4 cfm at 20 ft), you should probably use one diffuser. Running two diffusers with 0.7 cfm to each, I think would not be efficient use of each difuser. Ted can verify this.

The Vertex CoActive (dual) disc diffuser requires a minimum of 1 cfm. (.5 cfm per disc)

Sue or Ted
Ok I'm trying to zero in on what to purchase.
Would like to get a single disc diffuser, and a 100' of weighed hose. Can either of you give me specific modelspart no etc. that I can price out for near-future order? Don't mean to put anybody on the spot here! Thanks, Slydog

I sent some information to your mail address, Ted

Bill you are right that any single disc diffuser that has any lifting capacity to it requires more than .7 cfm This is where the synergystic effect comes into play.(two discs on the same station) As Sue stated the Vertex dual disc model "CoActive Airstation" lifts a tremendous amount of water with 1 cfm per station (two discs)The rating for example at 12 ft depth and 1 cfm is 2778 GPM.If you take one disc away or seperate them you will not be lifting 50% of the dual disc capacity. This is where I feel single discs get very compromised as they require a lot of volume (cfm) to do the same task. However they are a great unit for the waste water industry where huge volume blowers are used and the discs are in very shallow water as this is what these single discs were originally designed for.They also have larger slits in them and produce larger bubbles.There are diffusers designed for ponds and lakes and diffusers designed for the waste water industry and it is common to see the waste water disc diffusers being sold for pond and lake use.How can you tell the difference?? Always ask for the "data" on the lifting rates at different depths and different cfm's and or the OTR numbers (Oxygen Transfer Rates) if they dont exsist or they are "top secret" and or require several cfm per unit (4-7)then you are probably looking at a waste water bladder type disc.Lots of good posts on this topic.

Very good post Ted! By requesting this information on not only circulation rates but the Oxygen Transfer Rates, Standard Aeration Efficiency, Standard Head Loss (back pressure) all suggest that you are dealing with a company that prides itself on continually improving their product and ensuring that their customers are receiving the best piece of equipment on the market today. It also allows the customer to make an informed decision with real numbers and not just smoke and mirrors. We can provide these numbers for any customer that request them.

It would seem the GPM turnover rates at 1cfm at given depths is a common request when sizing a system. This is but one of several components that go into "properly" sizing a bottom diffused aeration system.We have posted these rates for the Aeration Technologies Inc "AirPod" and the Vertex CoActive Airstation on our website to better inform the pond owner in making decsions.I have received a few calls on my comments on waste water type diffusers and want to add this. A large pore single disc waste water diffuser can aerate a pond. The difference is the cost to do it. You can expect to use 4-7 cfm per diffuser where a few of the high performance diffusers on the market today will do the same job with 1 cfm per diffuser.The cost savings is in the initial pump cost and the electric consumption to run it and the overall maintainence cost.

Maybe someone has answered this before.

What does adding carbon in the form of saw dust do to a lake? This is a common action to reduce nitrogen on native prairies.