Troutgal - You have several complex issues going on in your shrimp pond.
1. I assume from your limited description and my limited understanding of our situation that you are a first-timer trying to raise shrimp/prawns on a semi-production-hobby basis.
Here are my initial thoughts.
A. A Koenders windmill is not intended for use in aquaculture crop production ponds that are highly eutrophic with large amounts of organics/wastes from the culture organisms, decaying uneaten food and tremendous numbers of other growing & naturally dying/decomposing organisms in a highly enriched habitat such as yours. The windmill is a good concept but not for situations like yours, unless you have 4 of them on your pond. Under the right conditions, even with 4 windmills, on a calm air night it can still result in exausted DO in the morning. You need aeration "over-kill" to produce high amounts of dependable compressed air to keep your entire pond constantly circulating. You have a crop here and do not want to lose it.
If I was in your situation, I would have a 3/4 hp rotary vane compressor that produces 9cfm at 2-3psi (4'-6' deep). Run it cheaper with 220V. This compressor initioal cost would have been less than the cost of the windmill. I would also have a 1/4 -1/3 hp rotary vane compressor or similar unit as a back up when the 3/4 is down for maintance/etc. Your gasoline unit sounds acceptble. I would use 3-4 membrane diffusers with the rotary vane unit to keep the pond circulating. In your small pond you MAY not need to run the 3/4 hp unit constantly but this run time would be based on numerous tests from various DO pond profiles throughout the growing season. Continual night and cloudy day running would I think be a necessity.
Shrimp willnot grow well in low DO conditions. In low DO they are too busy just trying to survive let alone grow. Better and stronger circulations will: 1 improve growth rates of shrimp, 2. increase production in pounds of shrimp, 3. improve muck digestion processing, 4. keep shrimp healthier and help improve final quality of product.
B. As Ted suggested, the shallow depth detracts from the circulation ability of any diffuser. All diffusers "work" better in deeper waters due to the characteristics of air lift technology. Not all diffusers are equal and in a case like yours you need the most efficient style; a crop is in the balance. You get minimal affect from a diffuser at 5 ft deep compared to one at 15ft deep and you have to compensate with more diffusers to get adeqate pond turnover and circulation esp in aquaculture production conditions. In your pond, you are approaching conditions of waste treatment rather than regular fish pond setting and should be using somewhat different concepts to facilitate the processing of all the organic wastes.
C. You are not adequately processing the organic waste. Proof of this is all the black muck that has built up during this past growing season. This muck turns black, does not decompose well and accumulates when it loses oxygen. Efficient processors of the muck need oxygen and lots of it. When oxygen is gone in the muck zone processors can NOT survive and do not operate; thus muck turns black and builds up.
D. Yes bacterial additions would help your situation
IF oxygen is present in all areas of muck accumulation. I would not soley rely on Aquatic Eco microbial products in your situation. I think you need better more specialized bacterial products. Check on Keeton Industries microbes at
www.keetonaquatics.com Jim Keeton has shrimp raising experience and is familiar with problems of shrimp raisers.
E. I would do some more homework this winter about shrimp raising. Now that you know more about some of your particular problems you can better quiz other shrimp raisers and educators. Check with your State univeristy extension specialist or other state specialists. For starters try past newsletters from Kentucky
www.aquanic.org/newsktrs/state/kentucky.htm and at
www.ksuaquaculture.org. Also remember to check into what other shrimp raisers use for emergency aeration. Bottom diffused aeration is VERY POOR for emergency aeration.
F. Next year to combat insect/invertebrate problems explore the dual crop concept. Research this and try adding some other type of fish that will help control the "bugs" and then be marketable at years end; maybe some fish for pond stocking or eating. Some raise minnows that are too small to eat the newly stocked shrimp, stock fish that do nte eat shrimp, or stock fish later after shrimp are too large to be a forage item.
G. Your real green water is typical of a production system like yours. The heavy bloom phytoplankton is very beneficial at adding oxygen to the water by day but it can be
deadly at night or during several days of cloudiness and then a night period or when the algae bloom crashes, esp in hot days of July or August. BE very cautious of late night and early morinig DO's during these periods.
H. Your problem of shrimp at the surface-water's edge was very proably a DO problem and had litle to do with shrimp seeking warmer water. Your advisor was naive and it was a poor conclusion esp when your DO reading was 2.0. DO was undoubtedly even lower in deeper water. Your shrimp won't lie about low DO.
Comments - Questions? PS When you reply please include:
1. your estimate of how much or how thick the muck was on the pond bottom,
2. how old the pond was or what muck was like at the start of the year.
3. How much feed you were adding to 1/4 ac per day.
) and I've come to discover that the pond ( 1/4 acre, max 5 ft. depth in low spot) is FILLED with this crap. I have a few questions:
