Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Can Tilapia do harm?

Hello all,

This is my first post here although I have been able to get a lot of good information browsing the forums. This is my first spring maintaining a 1/2 acre pond. My pond is about 30 yrs old and the previous owner never used any chemicals to treat the algae. Last summer I would get about 1/3rd of the pond covered in algae. I was all set to stock 10lbs of Tilapia until I went to my pond store for some unrelated items and asked what they thought about adding them to control the algae. They were totally against it. They told me a horror story about a customer of theirs that stocked them but was unable to harvest in time and they all sank at the end of the year and the Tilapia rotted on the bottom and ruined the pond. They did recommend Cutrine and muck pellets to get me started to control the algae. So I guess my long winded question is should I use Tilapia or chemicals?

Thanks,
Gklop

I'm no expert, but there are two factors I'd consider. First, are you putting fish food into the pond? If so, the tilapia will likely grow faster & reproduce more, which may not be what you want.

Second, do you have enough bass in the pond to keep tilapia populations under control? If not, this could be another reason to reconsider.

Just my two cents while I wait...and wait...and wait for the rain to stop falling!

Rainman, this post is a nice slow softball lob, hanging over the plate and just ready for you to swing....

gklop, welcome to the forum! Rainman is one of our local experts on tilapia and will help as will others I'm sure.

I'm from W Mi and tilapia will not overwinter in my pond so I'm sure some of them may die and settle, or be picked off by predators or turtles. I can't say if this is a good thing or a bad thing though...

What part of Ohio are you in? I'm assuming water temps get below 50.

What strain of tilapia where you looking to stock and my last question is, the customer that didn't 'harvest' in time, how were they thinking of harvesting them?

gklop, welcome to the site. I don't know much about fish but just wanted to welcome you. I put 8#s of mixed Talapia in my 1/4 acre puddle last yr. and once they reproduced, the FA was drastically reduced. Around mid Sept I trapped a few dozen and had my son overwinter them in his 55 gal aquarium. They've gone from around 2"s to as big as 8"s. I can't wait till the water warms enough ta get em back in the pond. My pond is predator heavy so that probably helped to keep there #s in check. I haven't had any water quality problems at all. If you put some in, you'll be able to monitor their #s as they aren't shy about comin to pellets. If you're worried that the scavengers won't clean em up well enough, come next Sept have some friends over and fish with Stubby Steves or sinking pellets. A long handled spear also works well at feeding time.

I do not plan on feeding. Just hoping they can reduce the algae. I've only seen a few bass around two pounds. There is a rather large school of black crappie that are pretty large and of course bluegill.

I'm in NW Ohio and planned on stocking Blue Tilapia.

I just realized that I didn't answer your last question. They did say that they tried to catch them with worms. I was planning on using fish traps and if not that using corn or dough balls.

This will be my 3rd year of stocking tilapia and I feel like they are at least a "2-fer" and in some cases a "3-fer". They help control algae, they are a high producing forage fish to fatten up the bass and take some pressure off the bluegill, and you can eat them.

I also heard the stories of mass die-off problems, but it has not happened to me. In Dec I usually see a hand-full of dead tilapia, but assume the catfish/turtles get the ones that die to the bottom and the coons and critters get the dead ones along the shore. I stock between 100-150 lbs of tilapia in a 4 acre pond and have had zero problems. I always ask for extra albino tilapia because you can watch them easier throughout the summer and fall.




Cutrine Plus granules have worked great for me and I use that too.

Gklop,

One of the things we try to do on this site is provide good solid empirical and scientific findings and knowledge.

There really doesn't seem to be a lot of main-stream research, but tilapia are used in many projects that get little exposure. These include everything from aquaponics to municipal sludge cleanup. The empirical evidence is pretty strong in their favor. In at least the last 5-10 years, we've seen very few downsides to the use of tilapia -- actually, I can't think of any.

I was one of several who fought hard to get tilapia legalized for pond use in West Virginia. There was fear they would get out of our ponds and become invasive species in public waters. It took a lot of convincing that tilapia cannot not survive winters in West Virginia, where open/public waters get well below the living conditions for tilapia. The only exceptions are very close to the expelled cooling water from a couple of very large power plants that use large water reservoirs for cooling.

I hate to say this, but most individuals in farm supply and other agriculture product outlets, have very little experience or education, involving aquaculture, especially pond/fish management. Yet, they are "trained" to be allowed to sell chemicals that can do far more harm than good.

Yes, there are good and safe chemicals. Many can be purchased without an applicator's license. But, there is a mindset where the recommended amount is perfect, a little more is better, and way too much is even better. Under the right circumstances, they work. It is the possible abuse/mis-use that becomes a major issue that can affect your pond for the rest of its life.

Tilapia don't fit that profile. They can live in horrible water conditions while cleaning them up. They die when the water gets cool. As they die, they add nutrients -- which your pond may not need at that time. But, if you choose at least a three year program of using them, those issues pretty much go away. The use of sterile (triploid) grass carp can also provide great benefit, as long as you don't add too many.

IMHO, there are far more positive upsides to using tilapia for pond maintenance and as forage fish, than there are downsides. It is also my opinion that it is far too easy to seriously damage your water source for a very long period of time with too much copper, or other chemicals.

Lastly, if you have a lot of algae, it means you have far more nutrients in your water than the pond can reasonably take up. It responds with an overgrowth of algae and other plant life. There are two solutions to this which should be balanced. Drop the level of nutrients getting into your pond -- like cleaning or diverting runoff water from a cattle pasture or other big nutrient source. The other half of the equation is to add enough plant life to your pond to absorb many of these nutrients. It could be floating islands, shallow water plantings, etc. That too has to balanced against the use of grass carp.

Ask a lot more questions.

I hope a few others will join this thread with pros and cons.

Ken

Ken,

Thanks for all the input. It's great to have this resource.

As far as where the excess nutrients are coming from, the only source I can see is the decaying leaves in the pond. Over the years the pond was surrounded by brush and trees. We have over the last few months removed about 90% of them. The only runoff that goes into the pond is from my property and there is no source for extra nutrients there. There is a horse pasture next door (100 yds) but there are berms in place.

The pond has few other weeds other than the algae. A little American pond weed and unfortunately a lot of Horsetail.

You mention a three year program. I realize that it's a balancing act and the previous owner let it go too far. I just don't want to start off on a path that is going to be too difficult to recover from if it doesn't work.

A little of topic but worth mentioning is that my pond is the water source for the house. Which is one reason that I am wary of using chemicals. I do have a well on the property but it is very high in hydrogen sulfide, which is very common in this area. It is normal practice around here to basically spray the well water into the pond and allow the gas to escape and then pull water to the house and treat it there. The previous owners never did this but the level of the pond was so low this spring I wanted to see if the pond would hold water up to the overflow.(Thankfully...so far so good.)

To add a little bit to Ken's statement...

" There are two solutions to this which should be balanced. Drop the level of nutrients getting into your pond -- like cleaning or diverting runoff water from a cattle pasture or other big nutrient source. The other half of the equation is to add enough plant life to your pond to absorb many of these nutrients. It could be floating islands, shallow water plantings, etc."

The FA comes from to much nutrients and when it dies adds back to the source. The Tilapia eat the FA, and if you catch them and take them out of the pond in the fall, you also reduce the nutrient level for the next cycle. That's a good thing. If they die, they might add back to the cycle, but most likely they will get eaten by stuff that will keep those nutrients form recycling.

----
I have had tilapia for two years now, and highly recommend them.

Natures clean up crew (raccoons, opossums, turkey vultures, etc) will also remove Tilapia from the pond. Yes, the excess nutrients most likely came from the decaying vegetation. There only two other ways to fight the algae problem.

Stocking Tilapia. They eat the FA, and are removed from the pond in the fall, either by you or by nature.

Put aluminum sulfate in the pond to bind up the P.

My vote goes to the Tilapia.

The horsetail is there because of the varying water levels. If you can keep the water at the same level, the horsetail will be out competed by other plants.

I have used two ways to control algae in my one acre pond without chemicals. The first was using 20 KOI, 6 Israeli carp. These are the algae eaters. I had enough bass that controlled the KOI & Israeli carp that I never seen one extra of these type of fish over many years. In addition to those fish I had grass carp to keep the excess water plants down. This is what that pond looked like.


When all of those fish were killed off in winter kill I redid my pond for algae control. It's all done with plants. In this makeover pond I have lots of plants, 7 grass carp for some underwater water plant control. I also have snails, clams and fathead and shiners minnows. the bottom of the pond is not disturbed with any bottom fish. The water is extremely clear. This pond bring in lots of wildlife.

In my last several years after introducing Blue Tilapia as a very viable pond management tool, I have had exactly ONE complaint about their activities.

The customer's kids wanted his sand beach area to NOT stink of hydrogen sulfide (hydrogen sulfide gas from anoxic waters under the sand). His kids "complained" they had to rake the nests that male tilapia made in the sand. I asked if the Tilapia cleaned the sand and removed the odor. He said yes, and that his kids just didn't like the nests. Seems to me, he just has lazy kids, since his water quality was improved.

I would LOVE to hear that story from the actual pond owner!!! I can virtually guarantee it never happened! Some dead tilapia do sink, yet unless something like a turtle tears open the body, it will eventually float as decay gasses make it buoyant. Then, terrestrial critters consume the body. It is simply NOT possible for the dead tilapia to "ruin" a pond from decay since (except for the pounds of fish added in stocking) there is no ADDED nutrient. The tilapia consume what nutrient is there already in the pond and convert it to flesh....there is no "new" nutrient created.

It is as much myth as the Illinois Conservation agent that likes telling people that Tilapia were in Lake Michigan and "babies" clogged up water intake pipes. I guess he confused Zebra Mussel horror stories with Tilapia....or, more likely, he has no clue how tilapia function and just needed a horror story to make up...

Thanks Rainman,

I have been researching all winter on the plan for my pond and thought I was all set in using Blue Tilapia as a strategic start in getting the pond cleaned up. I have come across many positive stories on using them and only a couple negative ones. When I heard one story in person it made me step back and reconsider. What I think I will do now is go ahead with the Blue Tilapia. My thinking is if at the end of the year when they die off and I can't get them out and they sink and add to the nutrient load the pond can still be recovered. If however I go with the copper, which I am sure will work, I can't really remove it.

On a related note, I also have two small Coy ponds on the property that are in pretty bad shape, lots of duckweed. I was thinking that once the Tilapia grow a bit would it be a good idea to catch a few and put them in these smaller ponds?

Thanks for all the input.

Ewest has encouraged response from "old timers" about subjects that have been addressed previously many times. I only share personal expereince.

Answering questions outside my regional area is off the table for me ...So...what am I doing on this tilapia thread involving mostly northern ponds? Sharing ideas with new southern pondsters that don't want to use chemicals to control aquatic vegetation.

The only experience I will share with my northern friends that struggle with pond shore line are goats - they will keep pond banks clean as a whistle!

Talking about Mozambique Tilapia to my Texas neighbors is preaching to the choir - we have taken them for granted for so many years with low stocking numbers at low cost, we take them for granted.
We do not and will not use chemecals on our ponds but that is a personal choice - GC when required.
Goats will wade into the water for primrose!

Good luck with your pond and welcome to PondBoss.
George Glazener

Here I go, ricocheting off in another direction. George, do you need to feed all those goats during the cold months, or are they able to browse for sustenance? That's quite the herd you have there!

Tony, I’m the city boy that “sharecrops” on my son’s country ponds…
He’s the goat rancher and I manage “our” ponds.
Yep, winter feeding is expensive - he has reduced the size of his herd considerably.

He’s got one young billy I’m gonna have to train the hard way - he was bottle trained and gets in my Mule for a fish food snack - got into cab of Todd’s fish truck and stupid goat wanted to go home with him..

These are my favorites:


How’s this for a Tilapia hi-jack?

George

gklop, as I was trying to say, there is no "new" nutrient load added when the fish die, even IF they sink and decompose. The nutrient was already in your pond and has simply been redistributed into a more edible form...Tilapia. Removal of all the Tilapia, without predators, is virtually impossible unless draining your pond, but many simply net them out of shallow areas when the water is cooling and the Tilapia are lethargic, sunning.

I just finished my first run through Ohio/Indiana and will be making my second run this weekend.

Copper Sulfate indeed kills algae, which decays quickly and becomes new algae in days to a couple weeks without feeding another plant, fish or animal to keep nutrients being utilized in a more beneficial way. Plus, you are adding a heavy metal to your pond sediments. (BTW, Tilapia will consume the detritus, muck, on the pond's bottom also)

Rex, wouldn't the "new" nutrient load (IF none of the dead Tilapia were removed from the pond) be the weight of the Tilapia (minus the water that their bodies are made up from) that were stocked into the pond?

i.e. if Tilapia is 80% water then the added nutrient load per pound of stocked Tilapia would be 3.2 ounces per pound of stocked fish?

Not in my opinion, because, except for the weight of originally stocked tilapia, all "new" Tilapia weight came from nutrients consumed in the pond...no net gain or loss of matter. It's just that the nutrient is in a changed form.

If you stocked 20 pounds in the half acre pond described in this thread, that 20# is the only additional load. All growth and reproduction is supported by currently present nutrient. If feeding fish, that would not be the case as the weight of feed would be a new nutrient load.

If you use Copper Sulfate to kill algae, there is no new nutrient load from the decay and regrowth. There is however, an increased BOD during the decay process.

I was wondering along the same lines. If I stocked 10 lbs of Tilapia, and they all died within 15 minutes of stocking, before eating any algae, then I would've added 10 lbs of additional organic nutrients into the pond.

If they survive and eat algae all summer before perishing in the fall, would I not still have that 10 lbs of nutrients (initial weight of the fish before they consumed any algae), to add into the equation? I can see where their offspring would begin to convert algae into body mass, but since I do not know the conversion ratio I don't know where to go with that. But the original stockers, would enter the picture with mass gained somewhere other than my pond, and when they die they will deposit that mass into my pond?

Course, that's splitting hairs pretty darn fine.


Shoot...had to pause to take care of some business, and Rex answered the question! Sorry!

I think both sides are correct about the nutrient budget when using tilapia unless someone can explain it another way. Tilapia are basically eating existing plants (algae-detritus) produced from the earlier nutrient concentration or recycling nutrient budget of the system. Granted nutrients can come from recycled nutrients, human inputs (stocked tilapia), and new nutrients from watershed inputs.

If one considers nutrients of the stocked biomass of tilapia then the same applies to any fish stocked - human nutrient inputs. However the apparent nutrient surge is primarily from the rapid decay of a large fish biomass.

If one sees evidence of increased fertility after the tilapia decompose it is not really so much the new external source nutrients but just a surge of nutrients from the decay of freshly decaying fish flesh that was produced from gradual production and consumption. The same basic thing happens when you have a fish kill and allow the dead fish to all decay & recycle at the same time. A spike or peak of available nutrients occurs due to a rapid decay and release (surge) of nutrients from those that were accumulated / bound in a large fish biomass and with a dieoff and a relatively rapid total consumer decomposition.

I would actually take that one step further. I think you need to account for the amount of nutrients that the fish expends in the form of energy. What they consume doesn't all go into the growth of the fish. I would think that swimming around for four or five months (depending on climate) would actually "burn" off nutrients. That energy has to come from somewhere.