Oct 26, 2009, 2:59 PM
Post #1 of 11
Malathion - fish lice & snail pests
I've posted questions before re my snail pest of wc my journey towards eradicating took me to using Malathion (57% EC).
My initial introduction to this pesticide was during my bout with fish lice- argulus. I used Masoten powder to dose them initially but turned to Malathion after reading the label that Masoten was an Organophosphate, similar to Malathion. My research took me to various websites advocating its use, even in this forum in a post by 'regallion' back in 2004, citing an article from www.bonniesplants.com. I presume regallion used it in his pond at the recommended dose of 2cc/1,000 gallons successfully.
As the rejoinder to that post was that "even minute quantities of this organophosphate can kill fish", I took to reading researches on carp toxicity levels and found that the acute toxicity level was at 9.0 Ál/L LC50. Translated to ponding lingo-koi will exhibit hyper-excitability at the acute toxic level of about 9ml/1,000L or 35.5ml/1,000gallons, where about 50% of the animals can die.
Armed with this knowleadge, I first tried malathion with my test fishes (3 local koi). I tried several dosages as follows;
1) 2ml/1,000 gallons
2) 5ml/1,000 gallons
3) 10ml/1,000 gallons
For all 3 dosages, I did not observe any excitability given the test kois were in the treated water for 3 days.
I then proceeded to dose malathion to my main pond of wc flashing was then a problem (fish lice present) and found that 5ml/1,000gals best worked for me in the initial 3x week dosing, dropping to 3ml the following 2 weeks. There were no more flashing or jumping observed from then on nor was there any physical evidence of lice. The procedure was to mix the malathion dose in a small bucket of water to dilute it first before introducing to the pond by slow addition and mixing. This is to avoid curious koi from being exposed to concentrated dilutions.
While dosing malathion on the 3rd week, I tried pouring the mixture to my vege filter where my snail pests where multiplying in the white stones. In one hour, the snails dropped from their hold on the stone. However, upon opening the water pumps, I observed the snails crawling happily again on the stones after 5 hours - guess they were just stunned during the initial contact. On the next dosing day, I left the malathion mixture on the vege filter for 6 hours before starting the water pump. This time, all the snails were dead! Talk about killing 2 birds with one stone, huh?
THough I am successful somewhat in my experiments, it would be best for others to use caution if attempting to replicate what I did.
I read in other websites (karl shoeler, koishack forum) where they are testing malathion usage at 2cc/100 gallons. I presume they used 50 to 57% concentration of malathion. At this dosage, its equivalent to 20ml/1,000 gals or double the dose of the experiment I conducted. They did 50% water change after 48hours and re-treated after 96 hours with a water change after the subsequent 48 hours. Hope to see what their final result would be.
As a final note, it will be a 'must' to continuously aerate the pond during malathion treatment as one research indicated that Oxygen consumption can be altered as a consequence of impairment in oxidative metabolism.
Would welcome challenges to my crude experimentation.
Regards to all.