Gambusia

Let’s first discuss mosquito dunks.

Floating Sustained-Release Larvicide For Long Term Control of Mosquito Larvae.

Mosquito Dunks or Bactimos Briquets are formulated to release effective levels of Bti for a period of 30 days or more under typical environmental conditions. The floating action of the briquets will ensure that the active material is released at the surface as well as gradually settle to the bottom. These briquets may be used in all types of mosquito breeding areas. To prevent briquets from being flushed out of certain treatment sites, they can be anchored using a string tied through the hole in the center or staked in place. Bactimos Briquets can also be used for pre-flood treatment. If the briquets are applied to dry areas which are known or suspected to become breeding sites when flooded, such as woodland pools and abandoned swimming pools, the briquets will float to the surface when flooding occurs and start releasing the active Bti material. Alternate wetting and drying will not reduce their effectiveness.

Applications

Mosquito Larvae: Flooded larvae breeding sites: Use one (1) Bactimos Briquet for up to 100 square feet of surface area, regardless of depth. In water with a high organic content, the application rate may have to be increased.

Pre-Flood Treatment: Apply one (1) Bactimos Briquet to each 100 square feet of dry bed surface which is known or a suspected breeding site when flooded.

Outdoor Use Around the Household: Bactimos Briquets can be broken into portions for use in many outdoor applications near the household, such as standing water in bird baths, old automobile tires, rain barrels, ponds, abandoned or unused swimming pools, ditches, tree holes, roof gutters for collecting rain water, flower pots or any other location near the household where water collects and remains for a period of time.

A simple search on the internet will provide countless companies that carry this product. I have seen this product at HOME DEPOT and many garden centers.

I have tried these in cement fountains that could not harbor the proper environment for small fish, and they did work well. The only downside was the dog drank some of the water - he looked a little queasy for a couple days and learned his lesson.

Now when it comes to fish that could control mosquito larvae, I found the drab colored gambusia minnows decimated the population in the back lily pond. Nothing much to look at, but efficient in function of riding the water of mosquito larvae.

The Mosquito Fish originates in the backwaters and freshwater ponds of North and Central America.  It is in the same family as the common guppy and is very similar in characteristics. The body is long and slender and is pale in color. The tail is moderate in size and does not contain any coloration.

You can differentiate the male and females easily. The males are smaller in size, have a pointed anal fin and are much thinner than the female. The females are larger in size, have a rounded anal fin, as well as a pregnancy patch on the lower portion of the body.

According to statistics cited in U.S. Navy research, a large female Gambusia is able to consume 225 larvae within a one hour period, and a pair of half-grown Gambusia are capable of consuming over 5000 larvae in 11 weeks. All sizes of Gambusia feed on mosquito larvae; even fry only a few hours old will attack young instars. Be warned that these fish also will consume fry of their own kind and of other fish species. These fast, aggressive fish will also beat up the fins of slower moving goldfishes when food sources run low- so keep an eye out for their tendency to fin-nip.

In late June of 2004, I had setup this lily pond and noticed within days of the water being added, THOUSANDS of larvae were in the water wiggling just beneath the surface of the water.

I added 6 goldfish in the 300 gallon pond. I noticed the numbers of larvae die back within 2 weeks, but concluded either more time or more goldies would be needed to get the larvae down to 0%.

I started to call around to learn more and see where I could acquire these Gambusia Minnows.

A friend of mine had mentioned she had noticed schools of dark colored minnows in the waters at Brackenridge Park. I had seen pictures and read about these little guys exactly as she described and took a trip to see if indeed it was the same species of minnow.

A couple hours later, a butterfly net and some bread proved all it took to collect a cup full of minnows. Now wild fish collecting can be risky in that you can introduce disease and pathogens from these wild fish to your pond stock, but since these guys were to be all to themselves in the lily pond, I figured let’s give it a shot. 

Upon the introduction of 20 small gambusia the population was non-existent within a week! Not a single larvae remained!

The lily pond with it’s calmer, shallow waters was perfect for adults to land and lay hundreds of eggs, but with these small fishes constantly on the lookout for them.

Talk about a BIO HAZARD - these natural mosquito larvae predators soon began reproducing at a alarming rate!

An out of control bio element I had added to eliminate one problem only to cause another.

I discovered each female could give birth to 20-50 live young a month! With the intense plant coverage to harbor larger surviving fry of gambusia, the numbers of these fish soared. With no larger fish to prey on the gambusia, their numbers rose unchecked further still.

My original 20 was well over 100 within the first month and a half. I was giving these fish to friends to put in controlled, smaller, environment water features like – water barrels and deeper fountains. I really did not mind the explosion of gambusia, but was glad it was just the 300 gal lily pond where they could be easier controlled if need be vs. the larger Koi pond.

When it comes to other’s experience with the fish some find they LOVE em’ or HATE em. Some have had to drain ponds completely to eradicate them, trying in vain to eradicate them with minnow traps. Other’s don’t mind their presence among the other fish - as larger Koi will gobble up some as well. For some reason, in certain ponds some fish keepers have a hard time keeping them - but a majority find these hardy fish almost indestructible, finding habitat in large ponds to small container ponds, doing what they do best - feeding almost exclusively on Mosquito Larva.

You will find the cooler months here in Texas will knock back populations to almost nil and spring invites their dominating return soon enough.

In reflection, I would say that a good amount of small goldies will efficiently solve your mosquito problem if you can’t get a hold of any species of gambusia.

With the facts presented it’s your call to cast these small fish as pest or assistant to your pond. ~ Now get out there and enjoy that pond!

Carlos Flannery