Could cannibalism contribute to a loss of about 10 fish in a 5 week period? We are down to 40 trout, and my students and I are concerned (and, admittedly, disappointed!) that the numbers dropped quicker that what we expected. It seemed drastic, but I guess that’s really only an average of two fish per week. We’ve only removed 5 dead fish since the beginning of Christmas break, which were small, the ones that remain look quite healthy and range in length from more than 3 cm ("Big Daddy") to about 2 cm. Still, I’d like some reassurance!
We perform weekly water changes of 20%, test the water daily, and feed them twice daily, we’ve also seen macroinvertebrates and new plant growth, leading me to believe that water chemistry is good. Yes? However, there is some agal growth; is it time to use the UV sterilizer?
Brian Cowden said:
January 16th, 2008 at 8:59 am
Diane,
Yes, cannibalism could account for such losses. If this becomes an issue, there are 3 possible remedies. One is to segregate the cannibal(s). A second is to feed more frequently, but not more food per feeding. Be careful as increased food will lead to more ammonia, nitrites, and nitrates, but if you are having good water chemistry then I suggest using this method. The 3rd possible remedy I call “the Soprano method”. Use your imagination!
At some point, cannibalism will taper off and end.
On the UV Sterilizer, I am leaving that decision to the individual schools. I am more and more of the mindset that it is unnecessary as it can also kill much of the good bacteria, but go ahead and try it. You can always turn it back off at any time. I will be looking for input from all teachers this year on this piece of equipment as I am considering eliminating it for the future TIC kits next year.