Pond Boss Forums AERATION Systems questions O.K. aeration experts...

For keeping a pond destratified and oxygen levels adequate in the deep water nothing beats the effectiveness of a bottom diffuser system and it's efficiency. Aware of that and do that. However I've always been taught as far as actual raw oxygen added to the water, and for use in an oxygen emergency they are not that good. In fact, cranking up a bottom diffuser in a situation where oxygen is becoming a problem can make it even worse for obvious reasons. Not a problem in a normal recreational pond where high fish carrying capacities are not raised, and a surface aerator is not only not needed, but can't do the same thing.

O.K. recently my algae bloom was getting out of hand in my 1/10th acre perch production pond, and some suggestions from a few fish farmers has me thinking I am not as knowledgeable as I thought I was. I had been running a diffuser in the middle of the perch production pond from day one, night and day at a really good boil. One fish farmer that didn't know I have the system running suggested adding a soaker hose connected to a compressor. Huh? Aren't I already doing something similar to that with my diffusers? Could the oxygen situation not have been as critical as I thought due to my running of the diffuser night and day at a good boil? Certainly much of the water column was being exposed to surface air. Heck maybe I don't even a surface aerator for emergencies as there never was one?

Yeah I know I could have checked D.O. levels with my meter but I don't trust my meter. It never stabilizes. I sent it in to Aquatic Ecosystems for a simple check up and they replaced the probe without asking me and sent me a bill for $250.00. I think it's the same probe.

Thoughts?

well i aint a expert, but the first thought that came to mind would be to use a surface or near surface circulator (like what shorty and bruce have shown before) in conjunction w/ the bottom diffuser. the greatest budget of oxygen influx occurs at the air/water surface (not at a bubble/water surface). by chopping the surface and circulating horizontally, then using the bottom diffuser to circulate (the oxygenated water) vertically, you cover all the bases.

my 2 c.

Yes Dave that's the plan pretty much. Diffuser will continue to run 24/7 and when the seechi dish says clarity has dropped below 12 inches or is approaching 12 inches the surface aerator is run at night. But my post was more of a question of basically was I not in as much trouble as I thought I was due to the diffuser running 24/7? Do they produce more oxygen than I give them credit for?

Cecil, I doubt you had any o2 problem. The bottom diffuser in my pond tripled my carrying capacity by oxygenating the lowerer depths ( average depth is 12 feet-25' max). They provide o2 to the entire pond not just the first few feet like most surface types.


I have no evidence to back up what else I am about to say.....it just seems to make sense to me.

I would think the use of a surface agitator (like a powerhouse)is the best for oxygen emergencies due to the instintive action of a fish "piping" at the surface when o2 is very low. Since the top film of water is always 100% saturated with o2, the rapid churning of the surface aerator should, in my mind, change that thin film to a few inches of saturated water very rapidly. IIRC surface aerators do very little for o2 below 4-5'.

You may be better off not paying attention to what is "in my mind"---It's usually filled with a playground of really cool stuff that will never work!----or costs a fortune!

FWIW, I decided to install a large bottom diffused system due to the fact that even with long cloudy spells, the deep water always has a very usable o2 sat. level that can be used up before going to critical o2 depletion.

Rainman thanks for the comments. However I'm still concerned the algae respirating at night could overwhelm the pond, or if there is a sudden crash. I will be ordering a surface aerator as insurance and at least the area around the aerator will be a refuge if things get too out of whack.

Insurance never hurts!

Cecil. you are approaching your situation correctly for your "potential" since you can have a great increase in BOD in smaller,high capacity waters very very quickly.If and when a bloom starts to crash bottom diffusers will not do much good but your surface unit may just save the day.I would also check to see that you maintain at least 80% saturation a foot or two off of the bottom and if not lift your water more times per day as long as increased temps are not an issue.As far as the soaker hose or that type of membrane I have not been able to get anyone to supply the OTR's or lifting data. My opinion is that if a severe bloom starts to crash that no matter how many diffusers you have or how many times the water is being turned the "potential" to have the O2 supply striped by the demand exsists,in that case the surface aerator is a great option to have.In a small pond the diffuser will then act to redistribute the super saturated water to all depths.

Thanks Ted!

Redistributing the supersaturated water to all depths during the day and evening lessens the chance of a DO crash. In these cases the likelyhood of DO crash increases dramatically with cloudy or overcast days or a rapid clearing of the water. Then one needs to be extra cautious and ready to react quickly with supplimental surface aeration. Being able to test the DO in unstable conditions is pretty important if one values the fish.

Right on Bill. I will be running the surface aerator AT LEAST every night and will see if I can get my D.O. meter running correctly. As you may surmise it may just be stubborn me when it comes to the meter.

In my opinion your subsurface diffuser should be sized to fit your application ensuring that you have good oxygen levels all the time. Doesn't it make sense to avoid the oxygen crash in the first place. This basically eliminates the need for a surface aerator. You may want a back up compressor or blower for an emergency power or motor failure but your aeration system should be sized according to your needs. I say this with the caveate that although our equipment has been used in many hatcheries I have never managed a fish farm and perhaps I'm over looking something. Somebody educate me if I'm bein' ignorant.

No you're not being ignorant. At least you won't hear that from me as I'm still learning. However the diffuser if anything is mixing the water more than enough. But in the event of a crash or at predawn when the prolific algae is respirating vs. making oxygen, mixing the water in the water column may not enough. I believe Ted explained the situation best along with Bill Cody. Intensive aquaculture with high carrying capacities has special problems not inherent in recreational ponds.

Well said Cecil (Ted and Bill). That needs to be repeated every day here. It is not limited to just aquaculture either. The more you feed and or have high fertility/productivity and have high fish densities the more that applies. Anytime you run the engine at high RPMs you increase the risk of a problem.

From the archives :

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=92440#Post92440 Pond carrying capacity

Topic: Trophic Continuum - natural to aquaculture --
http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=6;t=000162;p=1

"Bill and Ted"? Hmmmmm.

Abraham Lincoln in Bill and Teds Excellent Adventure:

Fourscore and...seven minutes ago... we, your forefathers, were brought forth upon a most excellent adventure conceived by our new friends, Bill... and Ted. These two great gentlemen are dedicated to a proposition which was true in my time, just as it's true today. Be excellent to each other. And... PARTY ON, DUDES!

Thanks for the comments and links everyone. I guess Bill nailed it with the term "unstable conditions."

Bill: So-crates - "The only true wisdom consists in knowing that you know nothing".

Ted: That's us, dude.

Ladies and Gentlemen,

(I presume Sue Cruz takes a peek at this category)

Please refer to this thread for an update. The science was good but it didn't apply to my situation after all.

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=128329#Post128329

Nice link Cecil. This is something we can all learn from. Out of curiosity, what type of diffusion are you using i.e. membrane, air stone, flex disc, etc..? I'm not asking for brand name, just style.

I use both membrane and stones. Unfortunately with diffusers in four ponds I can't remember which one this pond has.

These posts have got me thinking more about the application of aeration in aquaculture. Based on the apparent potential for an oxygen crash in an aquaculture situation it's obvious that high BOD is an issue. There has also been a lot of talk (historically) about the presedence of oxygen transfer at the pond surface as opposed to the oxygen transfer between the bubble and the water which is true. However, this topic is typically in the context of a recreational pond. It seems to me that in an ag/commercial application such as aquaculture that the water quality numbers might be approaching if not equal the strength of wastewater. In a wastewater application the oxygen transfer between bubble and water takes presedence due to the high BOD. Perhaps aeration systems for aquaculture applications should be designed with this mind meaning that a fine bubble diffuser might work better for this application when compared to a course bubble produced by an air stone or flex diffuser. Just me thinkin'. Anyone else have any thoughts on this?

Okay,

I have been away for a while here and many changes have happed with me that I will explain later, all for the better for me personally and for our customers.

WW...you are so right about the different application for aquaculture vs. a standard yard pond or lake. When sizing for aquaculter applicaions or "high density" fish applications we must use the 02 transfer through the bubble vs the standard suface air transfer.

We first must calculate the total oxygen requirements of the pond. The consumers of oxygen being as follows:

1. Fish
a. 0.45 pounds of oxygen/100 lbs of fish/day (warm water
spiecies)
b. 200 grams of Oxygen/KG of feed fed

2. BOD (Biochemical/Biological Oxygen Demand)
a. 5.29 grams of oxygen/kg of fish
b. Assume 70% removal rate of this 5.29 grams

3. Bacteria
a. 4.25 grams of oxygen/gram of ammonia denitrified
b. 13.1 grams of ammonia/lb of food fed

Example:

10,000 lbs of fish fed 2% of body weight/day

A. Fish Requirements
10,000 x 2% = 200 lbs of feed
200/2.2 = 90.9 kelograms of feed
90.0 x 200 = 18,182 grams of oxygen required

B. Bod Requirements
90.9 kg x 529 grams = 48,086 grams
30% x 48,086 = 14,426 grams

C. Bacteria
13.1 g x 200 lbs of food = 2620 grams ammonia
2620 grams ammonia x 4.25 grams oxygen = 11,135g

Total oxygen required =18,182 + 14426 + 11,135 = 43,743g
43,743/453.6 = 96.4 lbs of oxygen/200 lbs of feed

Once you know the total oxygen requirements of the fish, bacteria and Bod, then the numbers of OTR used from the diffusers to derrive at how many diffusers, and size of compressos will be required to meet these needs.

The point, anyone planning on doing any extensive aquaculture, cage culture or high density fish farming must take these numbers into play when sizing a system for their applications.

Good post everyone.

Boy being gone for a while, I just noticed my star rating dropped to a one-star...harsh.

Somebody must have made a mistake.

I just gave ya five.

Thank you Bruce!

It wasn't me! You're a five star in my book!

Me to. I wonder if that was a result of the puter changeover. 5 star in my book.

I just helped kick you back up. I got 5 stars when the format changed, and I have never allowed ratings. It must be counting my meaningful posts.

Why do I only have four stars?

Never mind don't answer that. It's probably the same reason I'm not a moderator.

Thanks All!

Any questions on what I posted? I know it is a lot of information to absorb, but it does show that more goes into sizing an aeration system than just making bubbles.

That is why I use the Bob Lusk question "what are your goals?"

5 more sent your way Cary.
Those low ratings must carry more weight than the high ones cause you still only have 4.

Bruce, Cecil, you got 5 too.

I gave Cary five stars too.

It looks like we have successfully stolen another post and changed it from aeration to stars.

I've noticed many of us have only one star, including all moderators. I was so confused about it that I PMed Bob and made sure that 1 was low and 5 was good. (It is). It appears that star ratings start out as a 1 until someone raises it. I am afraid to look at Lusk's. If he is a one we are all doomed.

Bing

Bing, you are right! I ran this post off in a different direction by accident. Lets see if I can get it back on track.

After totaling the amount of oxygen required, lets round that up to 100 mg/200 lbs of food fed, we need to match the total number of air diffusers to meet that need.

This is where knowing what your oxygen transfer rate of the diffuser comes into play vs. the gallons per min. for circulation like we use in a standard recreation pond.

Again you will need to know the lbs of fis, species and size and water depth.

A good reference for oxygen consumption for speciecs of fish in 02/hour/100 fish:

Coldwater Adults = 0.02 lbs
Warmwater Adults / Coldwater juvies = 0.03 lbs
Stripers = 0.04 lbs
Warmwater Juvies = 0.05 lbs

Number of diffusers required:

Lbs of Fish / 100 x Fish Requirements = x/diffuser 02 requirements = # of diffusers

Now match your compressor to the number of diffusers:

1.Diffuser requires ? of Cfm each.
2.CFM of Air x # of Diffusers = CFM Required from Compressor
3.Water Depth + Friction Loss in Tubing = Actual PSI requried.


I hope this gets this post back on track!

Hi Cary, great posts. What is your resource for the 02 requirements per species/size so that I may further educate myself?

Hi Richard,

It was the book of class notes by Cary Martin. Actually I have a binder I have kept since 1986 when I started college.

Since then every class, seminar, symposium and post on Pond Boss and even discussions with clients in the field, I have added my notes.

Most of the specific information came from a seminar I attended with Dr. Claud Boyd with Aburn. He does have a book out, that I will have to give you the title when I get back to my office next week. I also gathered some of this information from the following: "Handbook For Common Calculations In Finfish Aquaculture" by, Louisiana Agricultural Experiment Station. Louisiana State Universsity.

Maybe I should become a publisher and publish all of this info into one book. Too bad it would be only me to know how I wrote it down.

Thanks for the info Cary. If you remember, please send me the title of that book.

I have it marked in the calandar to send it to you. And again, spelling got me...Auburn, if I had a wish for the forum page that would be spell checker. I rely on it too much.

Ok guys, here goes. I am taking the smallest sump pump I can find, mounting it to a wooden bracket and using styrofoam for balance and bouyancy. I'm going to place the pump about two feet under the water. Coming out of my pump is a two inch hose, that will be reduce down (twice) to a 3/4 inch hose that will create additional pressure and use this sytsem as a horizontal aeration spray that will be about 8-10 inches under the water. Comments???? I'll let you know how this system works. Should create that "lazy river" flow that has been talked about. Wish me luck. JJ

Is it cost effective vs. a compressor designed for a diffuser? That is, how much power does it use and is it rated for continuous use? Personally I can't see anything as cost effective or efficient as moving water with rising air.

Idea will work, but in addition to what CB1 said, reducing the stream down to 3/4" hose will put additional stress/strain on the motor greater than its intended purpose, thus shortening its useful life. This could be verified with manufacturer's technical staff.

Not trying to be a naysayer but sump pumps don't have a lot of pressure either. Try hooking one up to a yard sprinkler and you will see what I mean.

When shopping for the sump pump, there was a contractor who made the same comment to me about "intended use". That, along with advice from this forum, has made me put that concept on hold. He thinks that by reducing the 2" down to 3/4" might put too much back pressure on the pump. Sooooooooooo, back to the drawing board. As usual, thanks guys, your're awesome. JJ

jimmydee-

I've been reading Pond Boss for some time now, and thought I'd finally chime in. My background is in large scale aquarium(upto and including public and institutional exhibits) design and construction.

I can tell you from experience that you will greatly reduce the efficacy of your sump pump and it's longevity by reducing the size of the return (outflow). If that idea is truly something your interested in, you'd be best fit to find a unit that is rated for high head pressure. These type of units are already designed with a smaller return than the suction (intake) side.

High flow units have the same size return as they do suction. These are not the ones you want if you're looking for high pressure out of the return.

Not to mention, as the guys already have, that moving water takes more energy than moving air. Water is heavier and takes more energy to move. Larger pumps require more electricity, which equals to more dollars out of your pocket. Moving air via compressor, takes a lot less energy, and moves the water for you as a desireable "side effect." (even though in our case it's actually the end result we're looking for from the start).

If there's anything I can help you with, please let me know. Good luck with whatever you decide.

Welcome to the forum, Doug. "Gold Coast", right?

Thanks Theo. Yeah. Pompano is on the Gold Coast, which is where I work. I live about 10 miles west of the beach.

The information here is endless. I always refer people to the site. It's a fantastic resource for anyone in the hobby or industry!!!

Welcome, Doug.

It's really good to have you here.

Bruce

Thanks Bruce. It's been an incredibly winding road to get to where I am now, but I really enjoy what I'm doing and am able to draw off of many aspects of my educational and work experience to help others.

I actually taught a few classes on photosynthesis, and water chemistry as it pertains to live coral propagation. I owned a coral farm that I sold a few years ago, where I would study the effects of waste materials, light period, and water flow on growth rates of corals and algae. Granted that was a marine application, but the information still applies.

What many people have in their pond situations is very similar to exceptionally large aquariums that are exposed to the elements, where conditions are a little more fluid (no pun intended). It took quite a bit of reading the posts here to see that, but the situations parallel each other quite closely.

I look forward to learning more about the issues people are facing and helping any way that I can. Thanks again for the warm welcome.