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Re: Anti-overflow hole in syphon is Oto killer

>  I haven't been surprised to find
>  a piece of leaf stuck there every now and then.  No big deal.  But this
>  morning I found one of my Otos stuck to the hole, trapped and killed by
>  the suction :(  The hole is about 3/16" (5mm) in diameter.  If it were
>  smaller, I think the problem might be even worse (higher suction?), if
>  it was larger, it could suck in the whole Oto.  I have blocked the hole
>  for now.  I think having a syphon-break hole is a generally good idea,
>  but it probably needs to be a screened hole, like the intake, to prevent
>  trapping or ingesting fish.   

I'm sorry you lost a fish, but I gotta disagree with your conclusions.  The 
force exerted by a vacuum is proportional to the area of the hole.  So, the 
smaller the hole, the smaller the suction.  A 3/16" hole has a cross section 
of (3/32) x (3/32) x 3.142, or about .028 square inch.  If your pump has a 
lift of 4 inches (probably not nearly that much) and if the intake screen 
were completely blocked, the maximum force that could be exerted through the 
3/16" orifice is about 
0.5 psig/foot_of_lift x 0.33 foot_of_lift x 0.028 square inches = 0.005 
pounds = about  0.075 ounce.  I really don't think this would be enough to 
trap a *live* fish.  The actual force would probably be much less, because 
some water will be entering the bottom screen of the intake tube.

If you are not convinced, drill several small vacuum break holes, so if one 
of them gets blocked, another one will break the vacuum.

best regards,