The 75gal reef tank cycle has started!!!!!!!

Well we're figuring that between the tank, sump and fuge that total water in the tank is about 100g total so a 20% water change would be about 20g which happens to be the size of the sump.
 
True... hmm.. you really don't want the water level in the tank to drop at all. It is unavoidable at times.. but once you get the nice purple coraline algae growing that the top of your tank, the second you lower the water level and expose the coraline to air you kill it, causing it to turn white. Then you have a nice white stripe around the top of your tank where you know you dropped the water level at one point.

I say do as much as your sump allows at most, and let the water level in the tank remain the same. If that means you can only do 18G instead of 20G, that is better IMO than doing 20G and dropping the water level in your tank. So, one week you may just go 6 days instead of 7 between water changes.. not that big of deal right?
 
Thanks for the answers.....Didn't know that even the simple thing such as water change can have so many different approaches to it.
 
Good point..I will have to discuss with him and possibly investigate how much the water level drops in the tank when power is shut off...if I'm remembering correctly I think it only drops 1/4" or so which in the whole scheme of things isn't that much...
 
Here is the deal. When we shut off the return pump the tank doesn't empty anymore then a 1/4" below the black trim at he top of the tank. I am not worried about this very small amount. I do not want to run the pump while doing a water change as it will shorten the life of the pump and if you also change, clean or disturb any filters the gunk that you wanted to get out of the tank will be put back in. You have to understand with the overflow that we have the water will only drain down to the top of the overflow box. Thank you guys and girls for all the advise and if you have anything else you want to know or share feel free.
 
Ya, that is fine if that is all the water level drops. Some people get a reverse syphon going that keeps sucking the water well below the overflow (had my tank drain 1/2 way onto the floor once because of that.. yet, another hard lesson learned).

Your setup you won't have the same problem I had.. but just remember, the second you expose coraline to air it dies.. within a second. Then, for months/years later you have a nice white bleached spot at the rim of your tank. Something you want to try and avoid if possible, but sometimes you just have to do it.. ie, something bad happens and you have to do a 30-40% water change in the tank.
 
Well between the sump and fuge that is about 29/30gal so if I have to do a 30%I would just take that out instead of the main tank. If it is more then that I would just do it twice over a day.
 
AquariaCentral.com