Pond Boss Forums AERATION Systems questions Sweetwater aerator?

I wanted to know if a Sweetwater Linear ll model SL94 is big enough for a .3 acre pond with max depth at 15 ft and average depth of 7 ft. It says it is for ponds up to 190 inches, but I can't find how large of a pond it will aerate. I have a friend who has one and it is really quiet opposed to a gast rotary that I was looking at.

dbw1968,

You will really be pushing the limits on a linear compressor at that depth and you have not even taken in that measurement the amount and size of supply line you will be using.

I would suggest upping to eaither a rotary vane and even then you can guarantee that you will be changing the vanes every year because of that pressure (6.6 psi just for the depth) or, go with a wobl piston compressor. They are quieter than a rotary vane.

Options like the type and size of a cabinet to house the compressor will greatly reduce the noise levels.

My friend has a sweetwater linear in his pond and it is the same size and depth as mine. He has it right by the pond so he is running the tubing about 75 ft. It seems to be working really well. How do you know if it is putting enough O2 in the water? He has a swath of about a 25 ft diameter of bubbles in the middle of his pond coming from a 9 in diffuser
Is this enough oxygen?

Cary,

Th sweetwater Linear compressor states that is a linear piston compressor. Is this good?

dbw1968 > Look at the psi to cfm curve on that pump as its listed (SL-94) 4.2 open flow 2 cfm @ 4 psi > 1 cfm @ 5.5 psi and 0 @ 7 psi, it states its good to 15 ft but is exhausted at that depth, I dont see that pump a good value as far as $$ for cfm at the diffuser,if you placed your diffuser at 10 ft you would have about 1 cfm available.As Cary suggests look into a vane or a wobl for a better value.Linears are great for shallower water but are the quietest pumps on the market.

Ted,

The early bird gets the worm, or in this case answered the question. 05:19...I hope you had your cup of coffee in your hand.

Ted is the numbers man. He nailed it on the the head that you will not have any volume of air available at the bottom pushing that much pressure.

Its like putting your finger over the end of a hose to get the water to shoot out farther. Of course if you do that you reduce the amount of water but the pressure is greater to shoot it out further.

"Linear Piston" the pump is magnet driven. It moves two pistons that operate diaphrams inside the pump. So, yes technically it is a piston but actually uses diaphrams to pressurize the air. Stick with a rotary vane or wobl piston.

dbw and Others - The bottom diffusers do not dissolve lots of oxygen into the water from all the bubbling action. They primarily MOVE poorly oxygenated water from the bottom to the surface where it can be reoxygenated mostly by phytoplankton near the surface. A small percentage of oxygen gets into the water by exposing the water to the air and agitation at the surface. See this post for more details why diffusers don't directly add much oxygen to water by the bubbling action.

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=7;t=000487;p=1

Bill, actually the water is mostly reoxygenated by exposure to the air at the surface, not neccessarily by phytoplankton near the surface. The more efficient the diffuser and the more water that is moved to the surface,the greater the lifting rate and turn over rate. The water is lifted from the bottom to the surface where it absorbs oxygen and releases gases and it continuosly layers out until the bottom water is back on the bottom again. The smaller the bubble the faster it moves and the more water it entranes to the surface. Bottom diffused aeration really is all about the lifting rate and circulation and the concept that dissolved oxygen is brought down to the bottom of the pond and through out the water column. It prevents stratification, eliminates the peaks and valleys and the bad kind of turn over that can kill your fish. Sometimes there are occurances that are out of everyone's control and oxygen is depleted faster than can be replaced by any type of aeration.

Sue - Good description how bottom aeration operates and I agree with everything you say above, BUT I take exception with: "actually the water is mostly reoxygenated by exposure to the air at the surface, not neccessarily by phytoplankton near the surface."

I am not sure how you arrived at believing this statement. Can you provide some proof? If you can provide some research or data then I will comment further about why phytoplankton is primarily responsible for oxygenating the surface waters compared to diffusion from the atmospheric air. "Reoxygenation of water by exposure to the air at the surface" has to occur primarily by diffusion unless you know of another method.

I think we need to hammer this one out, because I didn't do a good job of describing the phenomenon when I wrote the "aeration simplified" archived thread. Do we have specific literature on what appears to be a "surface diffusion vs. phytoplankton delivery" issue that needs resolved? If so I'll amend the archived thread so that it's more accurate. It's obvious that I don't fully understand the concept. I also just figured it was a air/water interface diffusion and hadn't considered phytoplanktons role.

If phytoplankton are responsible for exchange I assume that would be due to photosynthesis. How would this effect the efficiency of running aeration at night?

Hee, hee.

Good question.

GW - Yes. Addition of dissolved oxygen to water by phytoplankton, periphyton and rooted (submerged) plants is from photosythesis. Periphyton, FA, and submerged vascular plants add a big percentage but maybe not the largest percentage of the plant generated DO in the shallow and littoral zones. It depends. Phytoplankton can be very abundant in near-shore areas along with all the other plants. Light's penetration depth into the water plays a big role in this discussion. In open water (pelagic) zones (of primarily larger water bodies), phytoplankton for sure contributes the largest percentage of the plant produced DO. In small water and shallow water bodies, attached vegetation (algae and rooted) is often abundant and thus a big DO contributor. When estimating oxygen budgets of water, the proportion of littoral vs pelagic zones is important. Productivity (trophic status) and water transparency also play important roles in this topic because of the amount of plants present and ability of light to penetrate into the water.

GW asks- "How would this effect the efficiency of running aeration at night?" Surface disruption and bubbling activity is best at night because it does add some dissolved oxygen to the water. During night plant photosynthesis adds no oxygen to the water. Thus if one can add any extra DO, when photsynthesis is not occuring, it is good. Anytime you can add DO to the water of fish ponds it is good.

The main issue that I had with Sue's comment above of "the water is mostly reoxygenated by exposure to the air at the surface, not necessarily by phytoplankton" is primarily about which method adds the most DO to a pond or lake. I say phytoplankton (plants) and she says water's exposure to air at the surface (which has to be by diffusion). Do not take or use my discussion above as my answer to the debate.

Bruce asks "Do we have specific literature on what appears to be a "surface diffusion vs. phytoplankton delivery" issue that needs resolved?" There are no posts, discussions, or literature about which method adds the most DO to water or else they would have been referenced or cited. This thread may produce that info. I am waiting for Sue or someone to present her side of the debate.

I believe that I can end this debate. I JHAP being of sound mind do solemnly swear that I saw a TV program on the discovery channel in which it was clearly stated that 70 to 80 percent of Earths oxygen came from algae. It was on the Discovery channel so it must be true. I would have posted this factoid earlier (in fact I considered posting a thread on it after seeing the Discovery special) but I lapsed into an episode of dimentsia and forgot. 'Course now one of you scientific types are probably gonna point out that this has nothing to do with DO in a pond and that I should go back to drawing pictures of cows but Hey, I gave it a shot.

Jeff - it is a good start toward some second hand facts on this topic.

I think that the topic of using aeration needs to include the other values that it brings to your pond environment other than the discussion on added dissolved O2.
First of all you are stirring the water column so that you don't end up with a dead area caused by the thermal cline. Below that thermal cline is where the 02 levels get very low. In addition to added O2 in the various modes discussed in this topic the other very important point is that due to the stirring large volumes of the water are now exposed to the ultraviolet rays of the sun. That causes 2 additional benneficial events to occur. One is that the plant life that creats the O2 needs the light for photosynthesis which in turn then allows the plant life (phytoplankton) to create O2. Normally the life below the thermal cline is Anaerobic literally means without air. That life creates the fowl smell and lifeless zones that air breathing life needs. This stiring helps keep that anaerobic life in balance where light penetration is low.
The second very important factor is the effect of the Suns UV light on nutrients and other bad elements that develope as a result of resperation. The UV light breaks down these undesirable elemets in conjunction with the O2 that is in the water and then creates a very nice ecosystem for fish and man. If you have ever gone swimming in a lake or pond that has no aeration you may remember the slime that coated your skin. This just does not happen in a properly areated pond or lake.

Some extra notes about UV light in ponds. Typically UV light rarely penetrates any deeper than 3 ft into natural waters compared to deep penetration in distilled water. The amounts of dissolved organic carbon (DOC) in ponds and lakes strongly absorb UV light in the upper waters and DOCs limit how far the last 1% of the incident UV wavelengths will penetrate - sometimes only as deep as 2"-5". UV penetrates deeper when the water is salty than when it has low salts or minerals. UV rays will breakdown (photolysis) some chromophoric colored compounds into smaller biodegradable compounds and sometimes to even a complete degredation into carbon dioxide. Some non-chromophoric compounds which comprise a lot of the DOCs tend to be more stable, resistant to microbial breakdown, and thus they can accumulate in the presence of UV wavelengths.

Slime on your skin after swimming in ponds can come from numerous sources.