I've just set up a small aquaponics system using 50 gallon tanks,
Two for the growbeds above the one for the fish.
I only got the trout for the tank a couple of days ago and yesterday I started cutting some mild steel tubing to make a rocket stove on a bench about ten feet away.
Is it likely that the noise upset the fish, as this morning I found that two had leapt out of the tank. Whether it happened whillst I was doing the cutting or afterwards I don't know. The two trout were about 4" and 5" and they must have leapt out while the tank was full after the two growbeds had drained but the height they leapt was 6 or 8" to get out of the tank.
A more reasonable explanation is that they were were trying to catch a flying insect just outside the tank and I expect that this is what happened. I did expect to lose one or two fish with a new system but not that way.
I've fitted some glass over the potential escape areas which should eliminate the problem.
Fish have very sensitive sound listening organs. http://www.watertowndailytimes.com/article/20130519/COL10/705199942 half way down the page.
They essentially have ears that go from head to tail on both sides of their body.
I think that these lines can also sense changes in electrical fields. My fish don't much care for florescent ballasts turning on and off.
Fish are really quite sensitive to many things, sound and other vibrations, changes in light, pressure etc.
My second fish death was due to jumping out of a tank and that was with a cover over the tank and the fish still managed to find the gap. I find with the catfish that often when I get older larger fish in a tank and the numbers are somewhat reduced, the aggressive fish will chase other fish and I have lost a couple nice big fish due to them being chased out of the tank by even bigger fish
And it is sometimes amazing the ways fish can find to get themselves dead. Make sure all you plumbing and drains have grates to keep the fish out. and make sure that were the water falls into the tank has good high fish blockers since trout are known to sometimes try to swim up stream at the falls.
Thanks for the replies and the 'heads up' regarding other potential escape routes.
Being a newbie to Aquaponics I didn't anticipate the problem at all. I put some glass over the area where the first two jumped out but the following day another one leapt out from quite a small gap.
As a temporary measure I've secured a net curtain over the whole tank and the water from the external bell syphons falls through the net without problems, so I'll get some fine wire mesh for a more permanent solution.
It appears that it wasn't the noise from the angle grinder after all as I haven't used it since the first occurance but I did lose another fish.
Will need to pay another visit to the fish farm as soon as I block the other escape routes.