Maximum water change

often dignified

often dignified

AC Members
Nov 11, 2003
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Conneaut Lake, PA
What's the most water you should change? 10, 20, 30%?

I'm asking because my tank was infested with millions of tiny tiny air bubbles (I assume it's from my bio-wheel). Well I did a 30% change yesterday morning, and a 20% change at night, followed with another 20% today. I think I might have changed too much, but the bubbles are almost all gone.

My tap water and tank water are idential pH, hardness, etc., that's why I went along with that many changes.
 
I will likely be in the minority on this, but I honestly think you can change all of the water in a tank, provided the water paramaters between old and new water are identical, without causing a problem. This is because the nitrifying bacteria are housed in the filter media, substrate, and on surfaces of plant leaves, ornaments, filter tubes, etc, not in the water itself. That said, I'm not sure why you felt the need to do water changes to rid your tank of air bubbles (adding fresh water usually creates more bubbles ime).

Edit - I should add that I am not advocating 100% water changes! Different tanks get different water changes at my house. Big, messy cichlids get big messy water changes.
 
I've been battling these bubbles for a long time... it made the water look like milk and I was just fed up :p

They weren't the bubbles that float to the surface and pop... they were so tiny and just hovered around and danced in the current. I'm fairly certain that they weren't particles, I'm confident in my filtration.
 
The bubbles sound odd to me, I would agree with Una in that the bacteria is not housed in the water ( there is some there but very little by comparison to the media and substrate), The key here being that your tap water and tank water have identical PH and Hardness. Excessive water changes (I hate to use that term) can be detrimental because of the fluctuations they create in PH and Hardness. If there is no need to do a high percentage water change then don't do one, if there is a need, do it carefully. I have used and am a big fan of bio-wheels, and have never had one cause too many bubbles in a tank. Please let us know what you figure out or learn from this.
 
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If you do find the source of the bubbles, try and place filter floss in front of it. This will remove the bubbles before they enter the tank.
 
There is no maximum for water changes, so long as the replacement water is close in pH, temperature and GH/KH to the water removed. Many breeders do 100% or more partials daily, obviously without problems.

The only potential hazard to large volume changes is in not matching water parameters to the tank. Generally the larger and more frequent your partials, the closer your tank water will be to your water source parameters and the safer your partials will be.
 
tiny tiny bubbes that don't rise?

Is it possible that this is a bacterial bloom, not bubbles?

Does it look like someone poured a bit of milk into the tank?

someone jump in here, I've never actually seen a bacterial bloom!
 
They are just gas bubbles which will eventually go away with time. Water changes are great, a great tool for many things but they wont remove the bubbles in your water. :)

I like to do 50% water changes. If your Nitrate levels are below 20 ppm and your fish are healthy and thriving, there really isnt a reason to remove all the water. Like RTR mentioned, many discus breeders do 100% water changes but that is a special requirement, more so than the every day community tank.
 
i do 10-20% changes once or twice a week, depending on how busy i am, and how much i feel like hauling around my 5g bucket. i would say 20% once a week is probably ideal, but if my water was especially dirty, i wouldn't hesitate to change up to 50% of it.
 
Under normal circumstances (ie weekly water changes, normal maintenance), I usually do 25%-30% water changes.

When I'm changing water in a spawning tank for breeders or fry, I usually do 50% daily.
 
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