Two drain hole in overflow?

Exodon

Feeder Fish
Oct 26, 2013
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Georgia
Hi, everyone.

I've been lurking the forum for awhile now and finally decided to make my first post ;) main reason is because often time my questions have already been asked and answered (hooray the search engine). Though, I recently ran into a situation and could not find an existing thread similar.

Recently, I bought a used 75 gallon tank with corner overflow that comes with 3 drilled holes. Was wondering if I could use 2 holes to drain and 1 return? Or should I just plug one of the hole off? And what is the main purpose of having 3 drilled holes in an overflow instead of 2? Thanks in advance for your help!

Oh yeah, Im currently running freshwater with a 55gallon wet/dry sump.
 

ragin_cajun

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Sep 8, 2013
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duanes

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Agree about the protective redundancy, if you make each overflow tube slightly taller than the next, the chance of all 3 tubes becoming plugged at the same time, and an overflowing tank is reduced. And overflow tubes (especially 1, maybe 2), can easily get plugged with debris, plants, snails, a dead fish and cause an overflow, 3 is the insurance that gives you the time notice, and clean them out, before a problem gets out of control.
 
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