Plugging a drilled tank question

[CHOMPERS]

The glass patches on the outside are unnecessary. A single patch siliconed in place (with enough to cover the entire patch) will do. Unfortunately, if you change your mind in the future, the patches are a nightmare to get off. If you aren't feeling the pinch of the economy, I'd recommend bulkhead fittings with threaded plugs. That is the least permanent solution and will be the most adaptable down the road. If you later decide to try saltwater or a reef, you will already have the tank ready to go. (I swore off SW several times but I'm working on a 360g reef system.)

For what it's worth, saltwater and reef systems require higher flow rates (high current) than freshwater. The lower holes are for closed loop pump systems.

 

[Knowdafish]

i have successfully patched holes in several tanks. currently have 1 of those tanks set up and i patched it back in 1993. i got 2 squares of glass cut about 1/2 inch wider then the wholes i guess the glass is about 1/8 inch thick..glued it to 1 side with aquarium sealant. fill the whole with aquarium sealant and then glued the other piece of glass to the other side. it has worked on the 3 tanks i have done. i'm sure there is a better way, but my way worked well.

 

[CHOMPERS]

Oh, by the way, rubber stoppers isn't such a hot idea for plugging holes in a tank. Sure it will work and can go for years without a problem. The problem is it causes unnecessary stresses in the glass. Where this can work well for one person, it can be very unpredictable for another person. For instance, plugging one hole at the surface won't be a problem, but plugging two holes near each other and toward the bottom of the tank is a formula for sad days ahead.

Stresses are invisible in glass and only rear their ugly heads when the glass breaks. It is a summation toward eventual failure. The glass is only able to handle "X amount" of stress. The stress from the water, fish (impulses), careless handling & accidents, etc. all add up to the glass's stress/strain limit. The calculations to size the glass for the tank didn't take into account rubber plugs being crammed into holes.