evaporation rate and top offs

[dropped]

i'm trying to setup a auto-top off for my 20g sump. the sump is attached to my 65g tank with 2x250MH lights. I may have room for only a 1-2 gallon top-off tank. will that be enough or will i lose that much in a day? what's a good estimate for a week of evaporation? i know it's impossible to be accurate, but i need a ball park figure. thanks

[fishfreek]

YOu will proably lose that much per day. I lose about 5 gal a week on my 75 with just 440W of VHO. One thing that does affect evaporation is the amount of surface movment you have and if you have a glass cover over the tank.

[dropped]

thanks fishfreek, i was afraid of that. i won't be using a cover and i will have a mag9.5 with an scwd for circulation.

[indy]

I generally lose about a gallon a day with 110w of PC on my 55 w/10g sump, both uncovered. Been a little less the last few days, really humid around here this week.

[Brad]

I'm losing about 5 gallons per week from my 40gal system, including a 10gallon sump.

I use a simple powerhead attached to a timer pushing water through an irrigation dripper. The powerhead runs for about 6 x 2hrs each 24 hr period.