Pond Boss Forums AERATION Systems questions Ideal aeration schedule

I think I see where you are going with this. Are you saying running aeration during the day the plankton can add O2 to the entire column of water being moved by the aeration? The way I understood it, as soon as the water reaches the air/water interface the exchange happens and the water absorbs all the O2 it can hold. I am probably wrong, but I don't think you are getting any EXTRA O2 from the plankton. The air/water interface only affects the small amount of water at the surface but with aeration we are constantly exposing thousands of gallons to the surface and every ounce of water in that column that reaches the surface will end up fully oxygenated whether day or night. Great discussion!

Of course water temps, etc are really going to drive a pondmeister's decision to aerate during the day or night. It is still fun to discuss, all else being equal, is day or night more efficient.

I may just be completely over thinking the issue too!

I got another email from the company I bought my system from. Apparently they've never been asked the question about lift rate on any of their systems, but they were able to give me some numbers.

These are their words, not mine...
From what they relayed to me, my system is designed to produce 1.1 cfm at 30 feet. I'm set up at 8 feet, so I should be realizing every bit of what the pump is capable of. That being said....

1.1 cfm x 60 minutes = 66 cfh x 7.48 (cf of water) = 514.8 gallons per hour.

If I calculated my total pond gallons correctly, I've got approximately 187,000 gallons (60L x 60W x 7 avg depth (just a guess on avg depth) x 7.48).

If I'm lifting 515 gph that means I need to run 363 (187,000 ÷ 515) hours to get a single turnover!!??

I think I'm missing something because that just doesn't seem right with what I'm seeing temperature wise. I've reduced to running 6 hours for now (midnight to 6am) due to not having any thermocline and only 3 degrees variance from 20" to 10.5' (91 & 88 respectively) after only 3 days of running 12 hour shifts.

What part of this calculation am I missing? My goal is to run only as long as I need to, to get 1 complete turnover of the pond.

Somebody, please, help a fella out here.

I don't know the exact math but trying to equate the volume of water being moved to the volume of air on a 1:1 basis is incorrect. It may be proportional but it is more dependent on the bubble size and not just the air volume. Otherwise you wouldn't need a diffuser and could just stick the end of the hose in the pond.

In my case I have tubular ring diffusers. I too asked the supplier about lift rates and, not surprisingly, they didn't have an answer. Just a generic reply that it all depends on the exact situation. Based on the size of the upwelling when running they have to be moving at least several hundred GPM, if not more.

When I measured the temperature differences yesterday morning after running from 3am-7am they were within 1 degree at virtually all depths. With the system off at mid-day there was a 7 degree difference from the surface to 4 feet down.

This is all anecdotal of course (other than the temperatures) as I've no way to actually measure the volume of water being moved. I guess one could use a large diameter column and build a makeshift airlift and capture the water but that sounds like too much work.

Mike, I perused your calcs and they look good, but I think the "1.1 cfm at 30ft" must be the amount of air the pump will put out at a depth of 30 feet NOT the amount of water that it moves. It's just too small.

I know you know what you are asking for (lift rate), but I don't think your aeration company knows what your asking for.

OR the system is designed for a very small yard pond, but surely that is not the case since they spec it a 30 foot of water depth.

Also, for point of reference, Vertex shows with their lift rate chart that the volume of water that gets moved actually increases as the diffuser gets deeper. This is given that the minimum recommended amount of air flow is provided and other brand diffusers should be no different.

Tom makes a good point about the air flow to water flow ratio! I can estimate my ratio for a single vertex diffuser at 7 feet deep by the following...

7 foot deep yields 3.5 psi PLUS a little backpressure (1.5psi) from the length/size of tubing that I use PLUS 1 psi for the diffuser itself. In total = 6psi. This jives with the pressure gage on my system pretty close. From the chart below using the top right graph...



...we can see that my pump puts out about 4 CFM of air. That's the first part of the ratio. Using the Vertex chart above, my single diffuser would move about 1200 GPM at 7 feet deep. Converting to CFM...1200 GPM/7.48 G/CF = 160 CFM of water.


Ratio of Pump Air to Water Movement (in CFM at 7 feet deep) is 4:160 OR 1 to 40.

I'm not sure what this mumbo jumbo is good for unless you can somehow equate your diffuser to the vertex one and know the air flow at the depth of your diffuser.

One of the reasons I bought Vertex was the fact that they had some mumbo jumbo numbers to fiddle with cause that's what I do.

Do you have a pump chart? I am almost 100% sure it puts out more air at shallower depths and if we could somehow compare a bubble boil between yours and a vertex one we could guestimate the water movement, albeit very crude, but better than what the company has given you so far.

If the real goal is having decent DO levels at all depths then just measuring the temperatures at various depths may be a valid way to determine if complete turnover has occurred based on this post from Bill Cody a few months ago.

It's a long read but worth it if you haven't already seen it.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=30739#Post30739

Great old thread. Thanks for the link.

Cody: "The "when" to run it is ONLY a debatable issue if you can do a pond turnover in less than 12-18 hours."

Maybe Bill would grace us with an update to this 2005 thread comments.

Hey Noel,
Yes, the pump did come with a chart. I'll have to compare it to what you posted above to see how it corilates, when I get home this afternoon.

As far as boil, the immediate area of the boil looks to be about 3 foot in diameter, maybe 4, pushing water up at least an inch at the surface. When I looked at it this morning, the clean water line (no algae or film) was at least 40 feet in diameter. Thats encompassing all but the very outer 10 foot of the pond's banks.

At some point, I guess I'll need to plumb in an air gage so I can measure pressure at the pump. Right now it's straight lined in. Takes about 5 seconds max for the boil to erupt when the pump comes on.

My major concern, feeling like I've achieved complete turnover due to such a tight variance in temps, is trying not to over circulate so I'm not over heating the bottom of the pond. If I can get by with 6 hours, or even less to get the pond to saturate with O2, then in my thinking, that would be more beneficial from a temperature standpoint.

I'm going to get more temp readings today to see what the 6 hour cycle time has done. I may have to install a plate beneath the diffusers to try to reduce the amount of lift I'm pulling up from the bottom and see if that creates some cooler water at depth.

Good description regarding your boil, it painted the picture. It sounds very similar to mine. I'm not sure that I get 40 foot diameter clean water lines, but close. Keep in mind that I have 3 diffusers so the two shallow ones steal air from the main one. I would feel comfortable that using vertex's charts and/or your pump chart would yield close estimates wrt turnovers per day.

I've been looking for videos of the mixing effects and ran across this which may be enlightening. Not sure if it applies 100% but it was surprising how fast things mixed.

https://youtu.be/FE9VbiVbZFM?t=60

It's not a direct comparison due to the difference in the aerator design but still interesting.

I'm now thinking of adding some pond blue to my deep aerator airline to see what happens.

Hey Tom,
I just read thru the post you attached earlier. What I take from that discussion is, if you don't have a DO meter, then temps ranging less than 5 degrees from top to bottom is a relatively good method of determining O2 saturation throughout the area of the diffuser.

That being said, with a variance of only 3 degrees from 20" to 10.5' and a visibility of approx 24", I think my assumption of having a full turnover are validated.

This raises other questions for those of us with deep South ponds....

1) How warm is too warm?

I've found some postings elsewhere that say that 88-90 water is very tolerable by BG,LMB and RES, and I know GSF seem to like it hot as they are always right against the banks. I'm figuring most other species of panfish are just as tolerant to these temps as well. But when does it become unhealthy for all of our finned residents?

2) From a pond health standpoint, knowing warmer water holds less oxygen, how does warmer water affect the anaerobic digestion of detritus and accumulated muck?

That YouTube video sure does give you a good perspective on how bubbles influence water flow. I wish they'd done it with a single, centrally positioned diffuser.

I agree, great old thread and would be very interesting to hear Bill's thoughts almost 15 years later!

Great find, Thanks Tom

Noel,

I'm trying to make sense of this chart that came with my pump. If I'm understanding it, at 1.0 CFM (there's only one solid line) the pump is creating 7.9 psig. Without an air pressure gage, I've no idea what the pump is generating. So going with depth of 8.5', that's 4.25 psi on the diffuser. 50 ft of 3/8 line may create 1 psi, leaving 1.75 psi in excess, so I think I'm pushing some pretty reasonable air.

Looking at your vertex info sheet on diffusers, I'm not sure if I should compare to the single or double diffuser info. Mine is a double diffuser, but being tubular, I'm sure there is some variance as compared to a disk. For the sake of argument, I'll go with the single diffuser data.

At 8 feet, if I'm actually getting 1250 gpm of lift, that's 75000 gph. With 187000 gallons in the pond, I'm moving every bit of the pond in just under 3 hours. Everything being pure speculation.

Temp readings at 6pm registered 2 degrees difference between 20" and 10.5' (90 & 88 respectively). We've had cloud cover and rain on and off most of the day, so that contributed to the 1 degree drop at 20".

At this point, my question is still...how warm is too warm for both the fish and the pond as a whole?

Fish seem to be happy and fed like pirahna today.

Mike, sometimes it takes me several breaths and maybe some sleep to understand pump charts. So without noodling your chart...I would say you are on the right track. And using the lesser of the Vertex diffuser lift numbers keeps you on the safe side anyhow. In fact, throw in a goobery safety factor in of 1/2 and you are still turning your pond in six hours time.

Share your chart if you can post a pic of it, that will help. I bet your pump is a diaphragm or some sort of positive placement pump, like piston.

For some reason, my fish have backed off from feeding a fair bit lately and my water temps just 6 days ago were 78 top to bottom (they fed well then), but the summer heat came back and I am still at 78 on the bottom, but 84 at 18" down. The fact that your fish are eating well says a lot to me.

I need to find a host to get some pics on here. I've got a couple of plants I'd like some input on as well.

You are correct on the pump, its a Gast 1/8 hp diaphram, model DOA-P701-AA. Hopefully only running it 6 hours will give it a good long service life. The whole kit is marketed as EasyPro. I think it draws 4.2 amps, so a 6 hour run wont break the bank either!!

I've been pretty pleased with my fish, they're feeding well and growing. Looking forward to soaking some crickets soon and harvesting a few. Kinda torn about what size GSF to take out. They've been helping keep the fry and YOY in check. (And I'm kind of curious just how big I can get them). Seeing more and more 4-6" BG and a few over 7 now and lots of 3-5 inchers. GSF are as fat and sassy as ever and remarkably, still have a few nest tenders. Haven't seen much of my 3 LMB since I put the aeration in tho. Just a glimps of one every now and then.

I guess I need to quit being so anal about the temp and let the fish tell me how they're doing more. 88-91 doesn't seem to bother them much. All in all, the pond seems to be doing decent.

That is a neat video, thanks for posting it.

I will say that putting dye in a pond, even without aeration, it disperses amazingly quickly. I was surprised at how quickly it spread throughout the whole surface.

But I would suspect it only dispersed (without aeration) only near the surface or at least above the thermocline. That is what the vertical pumping of water of the aeration system does. Mixes the different density cold lower water with the upper lighter warmer water.

If you go swimming and approach the diffuser, on mine about 10-15 feet away you can feel the cold water difference as the diffused plume of bubbles brings up the cold water and it disperses across the surface just like the video shows.

I think wind (or lack thereof) also plays a big role. With no wind that cold water that surfaces could have the inclination to drop again as it moves away from the diffuser plume. But with any wind at all the surface current will quickly move it away from the plume. It is surprising how many and much current there is in a pond created by wind and also just by the sun warming. Dye would work well to show the currents. Even mud will do it. Mix up some clay in water and dump it in some area and watch natural currents disperse it.

This thread reads like you guys have things pretty well figured and calculated closely to what is really occurring with Mike's system.

The only thing I would add or modify to my prior post of several years ago is the amount of DO that is needed on the bottom sediment areas. I currently think 5ppm is more than adequate for good invertebrate and bacterial decomposition of bottom sediments. IMO Good decomposition of deep water sediments can occur in 1-2ppm dissolved oxygen at the sediment water interface in the pond's deepest water "belly". However if you want good fish diversity of all species living in the deep water area of the pond then 4-5ppm dissolved oxygen is needed.

Unless there are some specific questions I won't need to add anything else.

Thanks for chiming in Mr. Cody. Your insight of DO saturation at depth will be beneficial for any future considerations. If you could offer some of your experience regarding water temps, I for one, would be very grateful.

As stated earlier, I think I'm ok for now, but my concern is that I'm pushing the boundaries of what may be safe, temperature wise.

Short of infusing cooler well water into the pond, there's not much else I can do to reduce the heat if I'm going to aerate the pond. Being a small pond, some things happen much faster than on large BOWs, temps being the most obvious.

I guess my question would be how much can I reduce temps at once and not be detrimental?

I've got a small floating fountain which runs 24/7 so that keeps the surface water moving a bit on my small pond. I guess it also, at least in theory, helps reduce the water temperature through evaporative cooling. However I'm not sure if it might actually add to the heat load on extremely hot days.

That's my concern Tom. Eventually, the air temps may overpower the circulation and everything just keeps getting hotter over time and the whole pond overheats. At one time this summer my surface temps reached 99 degrees before I put in the system.

Running only 6 hrs at night, I've reduced the temp variance from top to bottom to only 3 degrees in just a week. That's why I'm thinking infusion of cooler well water may be my only option. I can maintain a full pond that way as well. Even with 10.5 feet of depth I'm 88 degrees on the bottom, 91 degrees 20" down.

You might try adding some additional shade, even if temporary. One idea would be to just throw in several 1/2" 4x8 sheets of the pink foam insulation to provide floating shade from the direct sun. They're not terribly expensive.

This summer is my 3rd year of running Kasco diffusers. The bottom of my 3+ acre pond has two different pool depths separated by a roadbed, ridge or whatever one wants to call it. Pool depths very during the summer but basically it is 10' and about an acre of it and 12' about a half acre depths for the most part with the remaining acreage running around 5' depths. My water temps ran 87 last year top to bottom and my Do ran between 5 and 6ppm. This year after watching facebook live with Mr Lusk I changed 4 diffusers and placed them off bottom or about 7 to 9' water depths. Now after doing this the water temps below those depths is about 8 to 10 degrees cooler. I have not been able to ck the DO because my meter probe is broken and waiting on another one to show up. But I will say, I have seen some improvement in fish activity over this summer and when running my fish finder I find fish from top to bottom in the pond. I think this setup is much better and I will keep it this way.

I was hoping that by elevating my diffusers they would create the same conditions you have Tracy, but it didn't. I didn't use the plate they provided as was kind of flimsy, and that may be why. The platform of milk crates allows water to be drawn up from below without anything there to block it. Even 22" up they still turn the whole pond over.

Think I'll find something to mount under the diffusers and see if that helps. Preferably something that won't try to float.

Tom,
I've been considering something along those lines too. Just don't know if I want to see big pink sheets floating on the pond. It's right outside the front door. Maybe some kind of floating island tho.