In article , "Flyboy" no spam
says...
Hello Everyone:

I have a 135 gal tank which is dormant (dry). I was in the hobby a few years
ago and gave it up. Now, I'm thinking about getting back into it and would
like to try something different. To get the flow I need, I'd like to drill a
hole (or two) in the bottom of the tank and build an overflow box
(internal).

Q1. Should I have two holes? (one on each side)

Q2. Should I have the return come back up through the overflow? (I was
thinking of putting the return on the other side of the tank)


Hmmm, exactly what I want to do also. Here is what I have learned:

A typical configuration for that size tank is an overflow in each back corner of
the tank, each with a 1" drain and 3/4 return. The return often has an adjustable
nozzle that can be directed toward the center of the tank so the water circulates
back to the overflow and does not just short circuit back into the intake.

Some manufacturers sell kits to equip their pre-drilled aquariums. For example,
you can take a look at the AGA Megaflow. It is in the AGA catalog and on-line, for
example go to DrsFosterAndSmith.com and search on overflow. What I have not seen
for sale is the overflow barrier with the toothed grate at the top. This piece is
fairly specific to the construction of the aquarium. The AGA kit is pretty
expensive. Barr Aquatic ( http://www.barraquatic.com/overflows.php ) sells
overflows for retrofit that mount differently but might work for you.

You could probably buy the bulkhead fittings ( thatfishplace.com ) and fashion a
standpipe ( http://www.dursostandpipes.com/ ) and spraybar with excellent results.
Some say that a 1" drain is marginal. Seems hard to believe, but the cost to step
up to 1.25" or 1.5" is small except for ball valves.

There is one detail that should be mentioned. Most (all ?) glass tanks of that
size have tempered bottoms that are not drillable. So I assume that you are
working with an acrylic tank ?

George