Donnie, sorry to read of your situation. I have gone back over the sizing specs that you provided last March 14th and will share with the group.I also have a call into you to go over this and should of talked to you by the time you read this. Your 185 x 75 oval shape pond would be 3/10 acre maximum, the water depth calculation supplied was 7-9 ft deep and I used an average depth of 6 ft even with your steep sides.The pump you have is a Thomas piston 1.5 cfm and is a slightly larger pump than the Econo 1 version we use when the pump is located pond side, this pump was used as it was to be located approx 150 ft from the pond. With an average depth of 6 ft and for this example lets round it up to an average of 8 ft to be safe you would have 780000 gallons of water and with a Vertex Coactive Airstation in 8 ft of water @ 1 cfm (yours would have more than 1 cfm) the lift would be 2300 gallon per minute or 3.3 million gallon per 24 hour day or 4.2 turns per day or just over 2 turns per 12 hour session.I also see in my notes that your water source is runoff from a neighbor that has 25 head of cattle and also the underground drainage goes into your pond.Since you are aerating and the DO was that low I am suspect that a planktonic bloom dieoff may have happened.Four turns per day is a lot of aeration and if a die off occurs turns of ten times this will not prevent a DO crash.Lets try to come up with some additional information to prevent this from happening again.Since the water temp was the same from top to bottom this indicates we have plenty of lift but something is crashing your DO when the reading is 1.75 as often I find that level without aeration.Did you do a check for DO in the top 6 inches as it should of been 70-100% saturated, if not very high in DO another indicator of an extreme demand out stripping the supply.Concentrate on the top two feet of water with anything that will splash (a lot)until the demand goes down.
