Pond Boss Forums INTRO Questions & Observations Observations On Oxygen

In the last seven years I've had three significant fish kills and four other times that I've lost a few fish from what I believed to be temporary periods of poor oxygen. I have six ponds total, and although all die offs are disappointing, I don't consider this statistic to be shocking or even surprising given the fact that I've sometimes exceeded recommended amounts of fish biomass in my ponds.

I've carefully documented all of the water and air conditions before and after all of these events, and I've found some commonalities that may be useful to others, but I'm especially interested to see if other pondmeisters have seen or heard of similar situations.

1. All seven times the water had recently become discolored.

2. Each time I had documented excellent clarity in the preceding weeks and significant macrophyte growth, in my case sago pondweed.

3. Sudden decrease in Secchi readings occurred right after massive loss of macrophyte viability. I.E. Rooted plants died, then water visibility decreased.

4. Right before loss of the macrophytes (Sago pondweed) once I had two days of significantly cloudy conditions, twice I had extremely windy and hot conditions. Three times I had just experienced 48 hours of nearly completely calm and very hot weather. The other time was in mid-October with typical cool, breezy conditions.

5. Each time I was given a forewarning, some of which I recognized and some of which I blissfully ignored.

A. Smallmouth bass swimming lazily near the shoreline with poor coloration.

B. No feeding for ten days.

C. No feeding for five days.

D. Dead grass carp.

E. Fish languishing near the shoreline.

F. No feeding for six days.

G. Dead grass carp again.

H. Grass carp parked like cars about two inches from the shoreline gulping.

6. The water is always brown during and for awhile after the fish kill.

Anyway, this is how I've pieced together the supposed events into something that makes sense.

A pond with generally clear water and no silt/runoff problems gets stocked with fish, then fed artificial feed. The nutrients are easily assimilated into rooted vegetation. The sago pondweed thrives, utilizing the phosphorous and nitrogen. Then some event precipitates death of the macrophytes, either change in weather, light levels, or water temperature leaving a lot of nutrients available for single-celled algae. The algae thrives but in it's massive numbers the water clarity is decreased and outcompetes itself. Suddenly you've got rotting vegetation in the form of macrophytes and microphytes inundating the entire water column, O2 levels crash and fish with higher oxygen needs like grass carp start to choke, leading to a cascade event of death and sadness.

Maybe this post could serve the purpose of throwing a red flag for another pondmeister about a potential dieoff, or maybe it could elicit a little discussion about my logic. I could be wrong about any or all of my assumptions.

Bruce,

Very interesting post. That's an average of one significant event per year. In over 25 years of managing several ponds here in Texas, I have never had one such event. Most of that time, no aeration was present in any ponds.

I have also allowed some ponds to push to and above the limits of bio mass, but for some reason have never seen an event like that. Perhaps its climate related. When it gets hot here, it stays hot. There is very little variation in water temps through out the growing season. I don't ever remember seeing a sudden drop in water temps either during a growing season.....even our thunderstorms are hot

Perhaps its related to a sudden change in water temps that "precipitates death of the macrophytes" and starts the chain reaction.

Very interesting topic to learn about...looking forward to reading responses from this great audience.

ML,

The good news is that only two of the seven events resulted in massive fish loss, and two other events resulted in the loss of fewer than ten fish. More good news is that it's been 22 months since the last biggie. There have been some instances where I've exceeded recommended biomass levels by 500% I really know how to go overboard! Someone once told me, "Bruce, you don't just push the envelope, you blow it up"!!

Bottom line is this: There's no way to tell where the line is in pond management until you've crossed it.

If you aren't living on the edge, you are just taking up space

Let's hear some great theories on Bruce's significant events!

Bruce, if you have six ponds, why do you push the fish limits so far to the extreme side of carrying capacity ? Do you have aeration in the ponds you're pushing past capacity ? Are you harvesting appropriate numbers annually ? Even if your fish kills are low, there could be many triggers for a die off at 500% of capacity. 500% is for fish farmers with filtration systems, you must like to play Russian Roulette with a loaded gun !

No, you are a Dentist...remember

ooohhh, now you are messing with me ! I know you had a post that said "I am a fish Farmer ! " Tricky guy

Bruce :

What does the brown water look like ? Is it a brown form of plankton? Greg refered to this as a red euglena bloom. We get it sometime when we have a green plankton die off in the warm season. It worries me because when it happens the pond activity falls rapidly. We have had no fish kills and the lakes are all over 6 acres. Greg stated that it is a sign of over ferility. Lately we have had this condition I think because of conditions like you described including the decay of dead pondweed which was sprayed but only about 1/2 acre spread out over a 16 acre pond. No aeration occurs but we have lots of wind caused wave action to aid in mixing. The lakes average deepth are about 9-10 ft. with little shallow water { less than 3 ft.}. What do you think-- any info here which helps ? ewest

I am a fish farmer. And I was aerating all ponds during dieoffs. I have one pond dedicated entirely to recreation and I'm maintaining biomass within normal limits. This pond is doing OK, but even this one had a kill three years ago, partly because of my greed to have the best fishing pond in Nebraska. It worked for a year or two, but when it crashed you could hear the noise for miles around. When I manage others' ponds I always make sure to keep overall biomass in check but I've learned more from my failures than about anything else. Hopefully age is tempering my enthusiasm. These fish kills though are still probably learning tools, and if I can ascertain the exact causes I can raise more fish. Maybe I'll even break even one year. :p

The brown color is definitely a form of LIVE algae. I know because I can actually watch it bloom on a daily basis. Every late summer I can watch my Secchi readings go from about 22 inches to 14 inches in six hours. It's pretty amazing. Unfortunately it also has a statistical correlation to fishies taking prolonged "naps".

Eastland, I don't know if I've mentioned this before, but my accountant has informed me that dentistry represents 105% of my income--and fish farming accounts for the rest.

OK, last post, and then I'll leave it to the Pro's to assist you. My last question...tongue in cheek, was it a "full moon" when they occurred ? Obviously that is rediculous (I think) but the better record keeping you do, the higher the odds are that you will find your answer...good luck, and I hope your patients don't start complaining that your hands smell like fish !!!

Is it Wednesday or Thursday? Bruce, I thought you were off on Wednesdays.

Anyway, besides the one excursion in October, what were the months of the other individual excursions?

I have a few thoughts:

1) Wow!

2) I bet with 25 inches annual rainfall you have very little flowthrough on the ponds most of the year. So all the nutrients added by feeding just accumulate. (All that seems pretty obvious.) If you're spending enough $ to run 6 ponds this aggressively, you should get the equipment to do every water quality test known to man. These will give you more data to judge how hard you can push the envelope. Personally I think 500% rated capacity is pushing way too hard (the Optimist says the glass is half full, the Pessimist says the glass is half empty, the Engineer says the glass was designed with a 100% safety factor, just about right); it doesn't matter what I think, but your ponds are thinking one event per year.

3) With 6 ponds, you should be able to run a control pond and an experimental pond, and note the effects resulting from the different stocking numbers/feeding strategies. Firestone I and II are pretty similar, right?

4) Wow!

Really bad events (3): Late June, late July and October

Moderate events (2): July and July

Minor kills but really stressed fish (2): August and August

Bruce :

Was the Oct. event caused by a rapid cold front induced turnover. If so then all the rest of the events sound like the same events I see here -- things look great then a quick green plankton dieoff followed by a brown plankton bloom and a crash in activity levels. Lucky no fish kills here. I will look into it more and report. ewest

Theo says: "The Optimist says the glass is half full, the Pessimist says the glass is half empty, the Engineer says the glass was designed with a 100% safety factor, just about right."

You forgot--The aquaculturist says that glass is half empty, and there's no oxygen in it, so I guess I'll have to grow ten channel cats in it.

I'm not currently pushing any of the ponds quite that hard right now, and my recreational pond is a downright joy to fish, but twice this summer I've had brown blooms and that funny "here we go" feeling that precedes dieoffs. Luckily I was able to subvert the problem with a little extra water. You're exactly right about the nutrient accumulation due to poor natural inflows. Actually no water escapes my property because all smaller ponds flow into the recreational pond, but the truth remains that nutrients build and build and build. Keep in mind though that the same applies to some of our other pondmeisters. Beware of the brown algae monster.

I've ordered lots of tests and my water always comes back with no red flags, but oxygen problems are fleeting and tricky to capture as data. O2 drops to zero and jumps back up to 5ppm sometimes in a couple of hours, and when you're at the farm only three times per week you have to be a little lucky to test at the right time. Once I had a company install a monitor that was running at the time of a kill and you could see the oxygen dropping a little every night. It was scary, like standing in a train tunnel watching the bright light getting bigger and bigger! (Now that was a little overly dramatic, wasn't it)?

Anyway, if this is going anywhere I completely forgot where. I'm loving any comments I can get.

Bruce, once long ago I (painfully) suffered through a number of Control Theory classes (surviving only because my roommate was a genius Control Major. But he couldn't spell or think in complete sentences.) A large portion of what I retain is that systems, wrt how they react to changes, can be overdamped, underdamped, or critically damped.

Overdamped systems are well behaved. They react to a change in inputs with slow, typically exponential changes which assymptotically approach their new steady state. An example would be taking a glass of ice water out the fridge. The temperature changes exponentially from 32 deg to room temp with no jerks or surprises.

Underdamped systems react to change with oscillations that slowly die out. An example would be the acceleration of a manaul transmission car with an inexperienced driver. You pop the clutch poorly, and it surges in jerks until it settles down in the new gear (at least that's what it was like when I learned to drive a stick).

Critically damped systems react to change with oscillations that do not settle down but rather increase in amplitude until the system is out of control. In school we ran a great example in Power Lab where we changed the damping on a motor until it was critically damped. At this point, the motor rpm oscillates up and down, farther each time until the motor is screaming and the circuit breakers on the power supply pop.

Your fluctuating Secchi readings with rapid, repeated algal blooms/crashes sounds like a system on the borderline bewtween underdamped and critically damped. I suspect if a real Control guy mapped out your pond system (the number of states for even a simple model scares the hell out of me - a 6 state system was too hard to handle 25 years ago and I suspect a simple pond model would need dozens of states), it would show that your O2 events occur when a pond oscillates out of control after going critically damped.

What does all this EE BS (from an MS, BSEE ) mean? 1) The more feedback you can get from your ponds, and the more often you get it, the better you can control them. 2) You need to "put the brakes on" and dampen the system. We know many of the things which help cause your oscillations: weather in all facets (can't control), fish populations (controllable), aeration and water turnover rate (controllable), nutrient input (largely controllable), nutrient removal (can't flush but could remove fish and/or plants therefore controllable). So you CAN manage these events, given the right combination of your available controls.

Interested parties can receive a summary of my MS thesis, "A Dynamic Simulation Study of a Computer-Controlled Quadruped Walking Machine." I will be very worried about any interested parties.

In my simple mind, I'm still betting that water temp change is the key parameter that sets in motion the chain of events that results in your fish kills. We are hot in Texas, but very stable...in temps that is.

Bruce,

It would not be very difficult to set up remote monitoring of your water temps. A few strategically placed sensors and a couple of sending units and you could monitor those temps right at your office on your pc...between drilling teeth.

Bruce :

Started below are sites with possible info on brown/red planktons .I will edit this as I find more. Very interesting info .

http://www.psaalgae.org/res/PALMER.pdf

http://ebiomedia.com/prod/algaeguide1.html

#4) Euglena were thought to be green algae; but turn out to be trypanosomes
(protozoa, like those that cause Sleeping Sickness!) whose "chloroplasts" were symbiotic green algae.

Euglena rubra - Red pigment protects this species of Euglena from ultraviolet radiation, which can cause a red "bloom" in ponds or lakes when the population suddenly increases.

Better look at this one below--text below is from it.

Euglena are single-celled animals with a single flagella. They can be common in very nutrient-rich waters like stock ponds and sewage lagoons. Water with Euglena blooms may appear bright pea green in color. Scientists recently confirmed a case where a particular species of Euglena caused a fish kill in a North Carolina fish farm. The species of Euglena that caused the fish kill can turn red during daylight hours, thereby causing a sort of freshwater "red tide".

http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/otherhab/

Pics. in this one
http://www.lakedoctors.com/weeds.cfm?wid=52&passtype=Algae

Last one for now.

http://www.lenntech.com/eutrophication-water-bodies/eutrophication-effects.htm

Not bad for a bucknut. If I understand you Theo, the peaks and valleys of the oscillations need to be cropped or smoothed. Bruce, you said you were aerating during the die offs. What is your explanation for this oxygen-rich zone failing to get the fish through the low O2 event?

Steve,

I have a long held theory based on just instincts...which is dangerous.

In salt water, there is a dreaded "red tide" of algae bloom that sometimes appears without warning to kill every fish in its path. It kills supposedly by DO crash. I have never believed that. The Gulf of Mexico is a fairly large body of water, sometimes called a pond, that I have trouble believing that the algae bloom alone can remove all oxygen to kill all fish over a large area of open Gulf water. My theory is that something else, in the algae itself, kills the fish, and we simply are not smart enough or "thinking out of the box" enough to discover it.

ML :

See my above above post on your red tide question. Still working on this. ewest

Theo! I'm impressed. I understood 42% of what you said. I'm about to read through it again. :p

Steve! That, my man, is the nagging question of the day. Why, why, why did the three most significant events occur while a pond was being aerated? My best guess comes from an understanding of what vortex aeration systems do. The typical compressor, diffuser system doesn't actually supply very much oxygen through the bubbles. All it does is increase the air/water interface for improved atmospheric O2 transfer. In the case of a massive phytoplankton crash, you may actually be experiencing a net oxygen loss by bringing up the most anoxic water from the bottom to mix with the so/so aerated water on the surface. Even the companies that sell aeration systems warn that they perform poorly in an emergency because their inability to infuse large amounts of O2. The reason aeration systems work so well for so many people is that they prevent the problem from occurring in the first place. In Theo's world, I'm overwhelming these ponds, pushing them to critical, and then, just maybe, the aeration works against me. I haven't run the aerator in my big recreational pond since October of '03 and I haven't lost a single fish. Coincidence? Could be, but I'll be darned if I'm gonna turn that aerator back on!