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Re: Too much oxygen

I do my water changes using an "automatic" changer made by Aquarium
Products. It turns out that it can be coaxed to double as a water
degassing device as well.

The changer is automatic in the sense that it empties and fills the 
tank at the same time, using a double hose and keeping the water level
constant. It works by squirting a fine water jet into the tank. In that
way it produces a constant flow rate that is almost independent from
the tap water pressure. Instead of letting the water jet squirt directly
into the tank and make a lot of disturbance, I place an old UGF riser
tube almost horizontaly on top of the tank braces, and position it such
as to intercept the water jet. The jet splashes violently inside the tube,
but since the flow rate is very low (about 12 gal/hour), at the other end
of the tube the water comes out almost totally degassed out, and just
trickles into the tank producing almost no surface disturbance (and no
bubbles in the tank).

I use just plain cold water from the tap (which BTW is soft) and add
AmQuel when I start the changer. The low flow rate allows the tank heater
 itself to take care of keeping the water temperature under tabs. Even in
the coldest winter days (here in Baltimore) I never saw the tank
temperature drop more than 0.5 degree F after one hour of running the 
device. This will of course depend on the heater and tank sizes. Mine is
150 watts in a 40 gal. water column tank.

The main drawback of such a device is that it is not practical to use
it to do large changes (50% or more) or to use it in larger tanks. 
By keeping a constant water level, the changed water volume depends 
logarithmically on the time it takes to change that volume. In my tank
it takes about 70 min to do a 30% change. To do a 60% change it  would 
take about 3 hours, and a 70% change 4 hours. A larger heater capacity,
or mixing hot water at the tap, would also be necessary in those cases.

BTW, I don't see as a drawback the fact that the device cannot be used
as a gravel vac. I only ocasionally clean the gravel, and very sparingly
using one of those battery-powered vacuums with a filter bag. 

-Ivo Busko
 Baltimore, MD