Water Changes Sticky - Help Unable to Follow Recommendations


It's me again. I had planned doing 15 percent water changes 3 times a week for several reasons. After reading the sticky thread about doing 50 percent water changes once a week - I confirmed that I cannot follow those directions.

"Make sure to match the new water temperature going into the tank to the water that is already in the tank within 1 or 2 degrees. You can purchase aquarium thermometers at a very low cost, usually under $3. Sudden temperature changes can be fatal to your fish, and may possibly lead to ICH."

I'm unable to do this as my husband (a longtime fishkeeper) believes in distilling the new water for at least 24 hours and our house is kept at 70 degrees, tank at 74. I had planned to very slowly add the water back in so my pH is not disturbed for reasons you'll see below.

"Check the pH of the aquarium water and the water from the tap before adding the new water. These should be matched as closely as possible. If the water in the aquarium is LOWER than the water coming from the tap, everything should be fine. I've never had an issue by increasing my pH levels.
If the water in the aquarium has a HIGHER pH value than that of the tap, add the new water slowly. Reason being, sudden changes in pH, especially drops in pH can be fatal to your fish."

My tap water pH is 7.6 but my tank water is 8.2 due to the substrate we chose. We didn't realize until after it was set up that the bag said can raise pH. Well it definitely did with ours. Even with an almost complete water change it went right back to 8.2. Rather than change the substrate we decided to just be meticulous about water condition. Yet another reason why we cannot do 50 percent water changes. Again, I need to add the water back in very, very slowly.

So after all that I just wanted to be sure that 15 percent water changes 3 times a week would be ok. It's almost 50 percent and given my parameters will be a lot less shocking to my fish and my pH.



50% water changes weekly is overkill in my opinion, it's more like 25% weekly. You could easily get away with only 2 15% water changes a week if you want to break it down into smaller, more frequent changes.

Another thing about pH as that as water "gasses off", it's pH will change as the CO2 is removed. That is your TRUE pH. Do you test your water before you put it in after leaving it for a day, or straight out of the tap?


Thank you. I test it after it sits for a day.


Racking, the 4 degree temp drop should not be an issue as you are mixing water close enough in temperature.

Regarding the difference in PH, have you tried keeping half a bucket full of used tank water around and adding half new water to see what PH value you register ?

Water change percentage has a lot of variables to consider, some keepers do large ones, some do small ones, some are done more frequently, some more sparingly.


I have and when it's out of the substrate it goes down. As soon as any water goes back into the tank it goes back to 8.2. Unless we empty the tank and change the substrate we just have to work around those parameters.

dont ever buy National Geographic Substrate! We bought it because it was very fine, rounded gravel for our intended Cory Cats and my husband didn't tell me the bag said it may raise your pH. I should have changed it before I got my fish and started cycling but it's too late now. Live and learn.

We'll with small water changes.



Have you tested the hardness of your tap and tank? I wouldn't worry about the pH difference because for complex chemical reasons Rivieraneo touched on, the pH of the tank probably wouldn't change much with a water change. The tank water is presumably quite hard. As long as the tap water isn't soft you should be ok. If you want to be extra safe add bicarb and Epsom salts to the tap water to bring KH and GH up to the same as the tank.

pH swings have always had a bad name for killing fish. We now know it's usually the change in hardness associated with them that does the damage.

It doesn't take long to change a substrate. Fish and plants in bucket with heater and filter, substrate out using a net or a square plastic container, substrate in using the same, filter heater and fish in, top up. Don't worry about bacteria, they're in the filter and not (hardly any) in the gravel. And as long as the new substrate is well cleaned and not Very cold, any organic cloudiness is nothing to worry about. The filter will clear it. Then clean the filter. Feed sparingly for a while..

IMO changing the substrate is the easiest option. It's only to do once.....

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