How To Perform Water Changes

This was written while I had a 75 gallon tank.

There are numerous opinions on water changes. They range from never doing it to very often in large quantities or even continously.
When I began this hobby I bought my RO/DI water from a local water purifying company and for the first eight months of my reef I was not very good at doing the monthly 10% water changes I had read and heard about. My reef did not do very well. Nothing seemed to really grow at all. My Zoanthids and mushrooms never grew new polyps and even the Xenias died.
At some point I got frustrated with the above issues on top of my incredible lack of coralline algae. This however I contribute to not being very good at keeping my calcium and alkalinity in desired ranges. Oh yes, when I began this hobby I was in way over my head.

After this too long period of time I began increasing the quantity of water changed and decrease the time between water changes. Since then my corals and coralline algae has show a very significant improvement. This has resulted in me performing biweekly 25 gallon water changes or about 25-30% of total system volume.

You need a few items for a water change. You need either a refractometer (left) or a hydrometer (right).
Either one will serve you well as long as you clean it well after every use. Personally I like the refractometer because it saves me time, it is more reliable and gives a more accurate reading.

My brand of salt at the time. I chose this only because it was cheap at the time. You can pick any brand you want. Just make sure it says that it is for saltwater aquariums.

Then you need a big bucket of water. I use a 25 gallon rubbermaid tub. Mix the salt in and let it sit overnight with a powerhead mixing the saltwater.
You are aiming for a salinity of 1.026. Try to match water change water parameters tank water parameters.

When I am ready I drain about 25 gallons of saltwater from my tank. This amount of water being drained causes some of my corals to be exposed to air for about 10 minutes. In nature they might sit in the sun for much longer during slack tide so I am not too concerned.

Here my Acropora loisettae is partially out of water.

Here a Montipora sp. also out of water. They are exposed to air a maximum of 10 minutes.

After dumping the old water I use a Magdrive 7 and a hose to add the newly mixed saltwater to the tank..

For an hour after this the tank looks a bit moody, but it clears up soon after and everything seems to have gotten used to this procedure. Even the green star polyp doesn't bother retracting its polyps anymore.