• Looking to buy a cephalopod? Check out Tomh's Cephs Forum, and this post in particular shares important info about our policies as it relates to responsible ceph-keeping.

Looking for a proper way to do water change?


Pygmy Octopus
Jul 13, 2007
I have an octopus in my tank. I am just wondering how I should do the water change. After I take out 20% of tank water, should I just pour in newly mixed salt water or I am suppose to pour in cycled salt water?
Most of us premix our saltwater and let it sit for a few days so the salt is totally dissolved either with an air pump or a filter in it. I for one have mixed and used saltwater immediately but have to be sure on temp, salinity etc.
Carol has given you some good information. You can safely use the water after a day of mixing with a pump (some say 12 hours). Be sure to test the newly mixed water for sg, pH and temperature. I've found the pH varies a lot and can only think that the salt mix doesn't distribute its chemicals evenly in the package.

Nancy, I don't think it has to do with distribution of chemicals in the bag - the industrial mixers they use on salt mix are pretty robust. PH vairies a lot due to CO2 in the water, though, so that may be the cause of the fluctuations you are seeing.

tfever, I suggest you get a container that holds the amount of water you are replacing. Fill it with RODI water, add an airstone for 02 or a powerhead to mix the salt (add it slowly and test often) and a heater and let it mix for a day. When all the levels are where you want them to be, do the water change. :biggrin2:
You have mentioned before that you like to use a heater to mix your salt and I can understand that raising the water temp would contribute to better suspension but do you have any issues with the salt coming back out of suspension when you cool it to tank temp or do you use very cold water to start and only heat to tank norm?
ahhh, I just realized you were in SF - does it ever get warm at night there?:biggrin2: My RO unit is in the garage and I have to bring in water to cool it in the summer :sagrin:
I actually just took my RODI off line and replaced it with sediment, carbon, carbon and two DI's. My tap water is like 40 TDS, and I wanted to stop wasting the massive amounts of waste water. So no more worries about temp for tank water until I mix salt in it!
What does your TDS unit read just running through the carbon and sediment filtration? My RO/DI unit is also sediment, carbon, carbon but with only 1 DI filter after the RO. I start with about 34 TDS after our dual sediment filters for the whole house (we get LOTS of mud and a visual on the RO/DI sediment filter tells me when all the sediment filters needs changing :hmm:) but I have never by-passed the RO unit to see what just the carbons take out. With the RO unit I end up with 4 TDS with clean filters (at 6 I replace them). The DI filtration I am using puts very little back into the water (unlike my prior DI sand) but I don't know which takes out more of the suspended metals and have no clue on how to test.
Our water is really muddy right now and the filter I put in last week (as well as replacing the whole house dual prefilters) is already showing lots of red mud. I am probably overdue for an RO filter change but have not worried about it since I have always shown about 4 ppm suspended stuff and it never occurred to me that it should actually be 0 (the check shows the same on two different meters so it is not the meter). I will give these guys a call before I replace the RO unit.