Big Water Changes


New member
When you do a water change on the big tanks do you just remove from the sump or from the display tank?

I have heard of simple changes with ball valves and separate pumps but how do those setups work? Any links to a good thread?



New member
I usually remove from the sump, but I guess it depends on how big your sump is *VS* the amount of water you want to remove. I typically do 20 gallon changes on my 125 and I can take all 20 gallons out of my 55 gallon sump after the return pump is turned off. If you completely drain your sump you'll obviously have to take from the display as well. I use a maxi-jet for transfering water. I'm sure you could plumb your setup to tee off of a return line as well.


sick yet brilliant
If you have water circulating through your sump it's just a matter of what is easier with the room you have.
I mix up some new salt water a day or two in advance, outside in a brute and fill my 3g water jugs. You can use any size you want, it's just easier for me to handle 3g vs 5.
I use my 12g top-off container filled with the new salt water, already connected to my ATO unit. I siphon water out from the display tank with a 1/2" tube covered with a screen. I am fortunate to have a drain built into my tank access panel behind the tank. The lost water is replaced with the ATO system. For my 120g display and 30g sump, I do this until I have emptied the top off container as many times as I wanted to, usually 2 or 3 times for a 24-30g change. It helps to have a buddy topping off the salt water so I don't have to stop the siphon or make a mess. Once I've replaced all the salt water, I refill my top off container with RODI to continue evap replacement.


New member
I have a diverting valve off the line going to the sump that I take from. It's just gravity fed so I don't have to worry about higher water pressures spraying water all over.


New member
10-15% water changes weekly are what many do...suggested using the sump as it cleans any detritus, doesn't change the water level in the DT, etc.


New member
I do a combination of draining water from sump/DT.. i change 50g a week my big tanks 175g/210g/215g (only the 215g is currently occupied due to a forth comming move).. i clean out the sump then drain the remainder of the water from the DT.. then i just pump the new water into the DT..water changes take aprox 30 min for each tank i do every sunday morning.. thats the perfect day for me no wife or kids at home and the dogs outside running off thier energy

I mix up my water on friday evening while my wife is watching her weekly show that i cannot stand.


New member
When I had the 75 gallon, I did my water changes by taking the water from the sump. I would just turn the skimmer up, and allow it to fill the 5 gallon bucket two or three times.


New member
i take the water from my sump because i do 100 gal at a time. it takes a while so i don't want my water level in my tank to be this low. also the sump is in the basement so all of the mess is in the basement and not on the hard wood floor.


New member
I take from my sump as well, unless I want to take advantage of the WC and siphon something out of the DT while i'm at it. I try and avoid disturbing the tank though, its nice because during a WC I can leave all the powerheads running and the fish or coral don't have a clue anything is going on.


New member
I siphon junk and dust from my 2 tanks and sump as the way to remove the old water PLUS remove junk at the same time.

there is always something to siphon somewhere until I have the right amount of water removed. no problem there. :D


New member
i usually drain my sump most of the way and take from the DT as well. I pull about 35 gallons out of my 125 gallon tank.


New member
I switch it up between my DT and my sump but favor using the sump. It all depends on which one I need to siphon something out of.