Pond Boss Forums AERATION Systems questions Fish Kill happening now. Aeration questions

We are the proud new owners of a 1.5 acre pond that is in the back yard of the house we bought in December. It is roughly 10+ft deep near the damn, but probably has an average depth of roughly 6 ft (estimating). Anyway, we had a pretty big algae bloom in the beginning of June. It has been hot and dry here leading up to this week when we had a solid 4-5 days of thick cloud cover and cool temps. It appears that the algae bloom has died as I do not see the little filaments in the water and the color has changed from greenish to brownish. I had noticed last weekend that the fishing did not seem normal. There was very little feeding activity in the evening and increased fry activity on the surface. I started to worry about oxygen levels. Well, yesterday I found probably 20 dead good sized bluegill and this morning 2 of our 6 grass carp have died as well as more bluegill, bass, and crappie. So something is up. The pond is spring fed, but the influx has not been keeping up with evaporation. The pond is 20 years old and I would estimate the biomass to be pretty high. Although, the grass carp have really cleaned up the thick moss around the edges over the past couple weeks.

There is the skinny. It appears to me to be an oxygen problem. So here is the question: What aeration system do I buy? I have read and heard good things about the hiblow pumps, but I am concerned about it having enough pressure for 10+ ft deep. I want whatever I do to be effective, but also I am in the middle of remodeling the house and have a lot farther to go, so spending more than I need to is ideal.

I am sure this has been covered at length in other topics, but I want to order my stuff today, not spend the entire day reading and second guessing myself. The pond is less than 40 ft from my shed, so power and housing a pump is not a problem.

Any idea? Thanks in advance!

Tony in KC

If you have a boat motor or a water pump, use that to stir the SURFACE water. Do not delay. I had the same thing start to happen last year, and stirred the surface with a 2" water pump, which saved my fish.

Should I not aerate? Or is this just a way to buy some time until I can get my system installed?

I would agitate the surface right away! Also, when you do get your aeration system installed, be sure to really research proper startup or you can make things worse in a hurry. Good luck!

Couple of things.

Remove dead fish from the water. Their decomposition will make things worse.

You can run new aeration full time if you put the diffusers no deeper than the thermocline. If you put the diffusers into cold deep water, slow startup procedures a must.

Tony,
First thing to know is how and where O2 is added to your water. It is at the surface. A bottom diffused aeration system moves the water to the surface where it can off gas and pick up O2. The boat motor will allow your water greater surface area/contact to pick up O2. Look up surface aeration. It is immediate and it is your best defense for a fish kill.

As for the hiblow pumps, they are used in sanitation ponds. In my opinion, they are the wrong pump for the job, but some have limited success with them. I wouldn't use one in water that is more than three feet deep. My two cents.

The startup process is critical as the bottom water contains a lot of toxic gases in solution that need time to off gas and little to no O2. If you turn your system on and walk away, you are guaranteed a massive fish kill.

tmilhon,
Whatever you can do to move surface water RIGHT NOW is a must. I had a similar situation to yours just a few weeks ago, tho not as drastic as yours. A trolling motor, outboard (yours or a friends), anything that will get the top 2 or 3 feet of water moving around the pond. The more you can chop up the surface, the better.

If nothing else, go to your local DIY store, buy a sump pump, a 5 gallon bucket, 2 feet of pvc pipe the same size as the discharge of the pump, and a 90. Make a "L" out of the pvc, attach it to the pump, drill the bucket full of holes to let water get in, set it in 2 feet of water with the pump inside. Be careful of the power cord plug not getting in the water. Let it pull water from that 2 foot depth and spray back into the pond. The important part is to agitate the surface as much as possible, as soon as possible.

tmilhon,

Please come back and let us know how things turn out for you. It is a tough row to hoe when your fish start to die. Hopefully the suggestions above will get you out of the woods and you can do some research on how to best aerate your water way. It is much easier to think things through when you are not stressed!

Ok. Thanks for all the replies. Here is a little more info. O2 gets into the pond from runoff, photosynthesis, and surface. We had 6 large grass carp and we experienced several cloudy days in a row. The pond is pretty protected from wind as well. Even 20+ mph wind does not produce white caps. I ran a hose from the discharge side of a shop vac and submerged the end of it this morning. Tooled around and fished out less than 200 fish, but 3 of the 6 grass carp. They are huge. I bet the longest one is close to 4ft. I then went to home Depot and got a 3000 gal/hr sump pump and rigged up the contraption that was suggested. It is running now. I will study up on start up procedures, but what pump and diffuser would you guys recommend? I am thinking a rotary veined Gast that will do 10 psi. Housing it is no problem, electricity is no problem. I just want to know some opinions of those who have already been down this road.

Thanks again!

You may have a few dead or dying fish turn up for a couple more days. After my low oxygen event last year on June 19, I watched carefully and netted the few channel catfish that came to the top distressed, and cleaned them before they died. The distressed ones were all channel cats over two pounds. No bluegill were lost that I know of. The big ones seem to distress first. I only lost a few in the end.

Well, I just finished disposing of the kill from today. It was 4 large wagon loads. Although 1 wagon load only had 3 giant grass carp. Probably 10 nice bass, 1 probably 8-10 lb channel cat and well over 100 blue Gill. We have a pretty good crappie population, and I didn't see any of those. Hopefully the coons, coyotes, and foxes make quick work of their treats. What aeration pumps are you guys using? I want to get this stuff ordered so it gets here in time to make a difference.

I can't give you any direction regarding an aeration system. I'm still trying to figure that one out myself. I do know with your pond's depth, 10psi will be more than sufficient. You'll find a lot of info here, but it's trying to cipher through it all that gets challenging. I think it's more about CFM than PSI. The key, I think, is the diffuser and finding one that won't create too much back pressure on the pump at the depth you decide to set it. Considering 1/2# of pressure for every foot you drop, 10 feet would only require a pump capable of 5psi. The Gast 0523 seems to be a pretty popular unit, but go with what your budget can handle.

Keep us in the loop on how the sump pump is working for you.

Well, I only found a couple dead this morning, but they easily could have been missed yesterday. I think I am dealing with more of a turnover event than sustained low DO. It was mid 90s for a week followed by a week of low 80s and one day with a high of 70. It was a great break from the heat, but that combined with the clouds could have been the right mix of problems. I think aerating will benefit my pond long term, I am still trying to figure out my system though.Also, it seems that aerating during the day would be best to mix the bad bottom water with as much DO as possible right?

I have found that aeration is best done opposite of the high or extreme temps.
For example, it's 90 degrees out today during the day, so i aerate at night when it's in the 70's to avoid superheating the water.
Same deal in the winter. I aerate in the day to avoid super cooling the warmer bottom water.
(winter aeration is really not needed in my area.)

Question- does your pond have plants in it? That may be a quick way to increase your dissolved 02 levels until you can get an aerator installed.

Not many plants, but as 3 of the 6 grass carp have died, I would expect plant life to increase. Does duck weed add DO?

I have found some kits online that seem like a good start. They always seem to be twin piston compressors though instead of the rotary gast pumps. Any reason not to go with a pistol style compressor?

I bought a diaphragm style septic pump.
It's working great in my 8' pond.
I am glad I went with this type pump $ wise. It's easily rebuilt, quiet and efficient.

So, my pond is shaped like a three toed paw print. The middle "tow" is very shallow. 3ft at the mouth gets down to 1 ft pretty quick. Another inlet is probably 4 ft deep and run off feeds in during big rains. The last inlet is probably twice the size of the other 2, I would estimate 5-6 ft at it's deepest, and is spring feed, as well as tied into the pretty large watershed above the pond. The main body of the pond is 10+ feet deep near the damn. I was thinking of getting a kit from eBay that has a 3/4 hp twin piston compressor and 4 ring difussers. I can house the pump in my shed and run a pex line to the water's edge and have a post where I can have valves for the 4 supply lines going out to the difussers. I thought I could put a diffuser in each inlet and 1 in the deepest part of the pond. I am wondering though if the 2 smaller inlets even need one. The fish kill happened mostly up in the shallower water, but I figure the fish were looking for better water and just ran out of places to go. Anyone have any direction on the above plans?

Sounds like a good plan. Just make sure you cover any PEX that is exposed to sunlight. Simple pipe insulation will work PEX will deteriorate if the sun stays on it.

I think your assumption is correct. They all went to the shallows looking for O2.

I found a demo model gast 1023 for $250. Seems like a great deal, but at 10 cfm, is that too much air flow?

I don't think you can get too much air flow, within reason. The bubbles are used strictly to create an upwelling current. Others will know more.

I'm using a 1023 with three 9" double diffusers on a 3 acre pond running about 8 hours a day and it works well.

If I recall correctly on the 9" diffusers I am using two (one double Matala diffuser) will not quite handle the volume of air the 1023 puts out. In other words it would over pressure a double 9" diffuser at a 9' depth.

So with the 9" Matala diffusers I should not use it on less than three of the diffuser heads at once. I normally run it on 6 at once (three doubles).

I would say if you had anything over an acre pond you could make it work with three diffusers. You would just run it fewer hours. So you would need a timer capable of starting a 1hp motor which is what I have.

Running fewer hours per day just means the pump will last more years.

I am thinking about just running one vertex xl5 diffuser with the 1023 providing the air. I would probably be in 9-10 ft of water and that diffuser should move about 10,000 gpm! There are three small inlets in my pond, but they are shallow and one of them (the deepest) is spring fed. What I save in air line cost I will spend in the diffuser, but I figure this would be a good core to start with and it will move all the water in the pond overnight. The pond is shaped like a three toed paw print. Most of the water is in the main body. I realize that I may not get very good turn over in the little inlets, but it is shallow enough I am not sure it will matter too much if I turn the main body over every night. Is this a good way to go or is it better to spread out less efficient diffusers? I would like to order everything today and get this project going!

Duckweed isn't good for adding DO to your pond. Much of its released oxygen might go directly to the air. Furthermore it shelters water from disturbance and it shades water preventing photosynthetic activity below. On its own, it can cause DO problems and if you have a lot you should develop a plan for controlling it.

It's not covering any significant portion of the pond yet. Just wondering if it was helping or hurting.