How I Do Reef Tank Water Changes

I guess for most people this is not what I would call an exciting subject. Just remember, there are people out there entering the hobby who really don't know about any type of tank upkeep, and really need to know, before they buy their first fish. This may help them know what they are in for. So here it is, in all its glory!


In my case, its a bit more complicated as the systems are linked to a common sump. Pictured left is the Alpha reef. I don't have to do anything with it during this change, since I'm pulling water out of the 55 gallon Beta reef that is linked to it. The Alpha's water level will remain the same. This is a good thing, as I could only drain a few gallons at best before exposing corals to the air for an extended period of time. I make sure the return pump to the Beta tank (the one I'm changing water on) is off. I also close the ball valve to stop any water draining from the Beta tank back into the sump. This helps keep the water level higher in the Beta, and keeps the inhabitants happier. If it let the Beta tank drain down until it stopped going into the sump, then remove 20 more gallons, the fish would be pi$$e%! I'd probably only have 20 gallons in the tank after all that, which would be about 6 inches of water. Not a good thing with big fish...
This is the shared sump. This is where both return pumps live. Both tanks drain into here. This allows me to change water and the main tank (the 90 gallon Alpha Reef) never knows its happening. It just noticed the water get slowly better after the change is done.
I usually don't do more than 20 gallons at a time. I place an empty container next to one full of new salt water. The new water is about 20 gallons of RO/DI water. I then add a powerhead and a heater to it, as well as the approximate amount of salt, and let it go for 24 hours, then add a bit of salt as needed to hit 1.026/1.027 as read by the refractometere. This waiting period will make sure the salts fully dissolve, and also I wont be pouring 20 gallons of 70 degree water into a tank I maintain at 80. In emergencies, you could forgo the 24 wait, but the temperature is a big issue!
Just a shot of the 55 gallon beta reef draining. Wee!
Still draining...Notice that this tank does not have corals going all the way to the water line. This allows me to do this without bothering any corals, and also gives good room for the 3 large fish that live in here. It still annoys the fish, but they get over it quickly.
Ok, 20 gallons removed. Time to refill
Since I only use a Hagen 400 powerhead to pump water back into the tank, I need to give it a booster chair, otherwise it would take a week to refill! Let me explain this further. Most pumps are rated at a gph (gallon per hour) with a certain head pressure (how far it had to push it upward). If the container was on the floor, the head pressure would be about 4.5 feet. This is just too much gravity to fight with for such a small pump. Boosting it up about 2 feet makes a huge difference. Be sure to check the head height gph stats on any pumps you plan on using for pushing water up, and not just in and out for current.


That is about it. This may be a waste of space, but who knows, someone may get a gleam in their eye and say hey! Now I know a better way than just dumping 20 gallons into my tank from a bucket! To tell the truth, this would have helped me a few years ago. I think that is why I put up many of my basic answers and projects. You just never know who is reading, what level of experience they have, and what they haven't thought about ahead of time.