s after water change

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105man

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Aug 27, 2003
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I have had a 30 gallon community tank with a variety of easy, hardy fish doing well. I recently did a water change, using distilled water. This water change may have been a little larger than usual. I do not change the Whisper biobag when I do a water change. I usually wait to do that at another time.

Shortly after, both of my little gold dust mollies and the cobalt dwarf gourami died around the same time. None of the other fish...platies, rasbora, orange dwarf gourami, clown loaches...had any problems at all.

Any ideas about what happened? I have used distilled water for most of my water changes for quite a while, with no prior problems.

Thanks.
 
If you are using ONLY distilled water, then you are headed to permanent problems. You need to mix this with at least SOME tap water. There is very little hardness or alkalinity (to resist pH changes) in distilled water. Your pH may have dropped rapidly since that last water change (or raise rapidly because of the water change) and stressed some of the fish! I'd always add maybe 10% to 50% tap water, even in a soft water tank. Try different amounts and check KH (Alkalinity) and pH regularly to see it it is changing right after or right before a water change! Check the difference.
 
I agree with Bmeasure, probably a PH crash... Were you using straight tap water before the last water change, or have you been using distilled water?
 
Sorry, just re-read your post and answered my question. Not a good idea to use straight distilled water. Any reason your not using treated tap water?
 
Research OLD Tank Syndrome,

Bmeasure Hit the nail on the head. Have you done a PH test. judging from what you've said so far, I would guess your tank PH somewhere between 5-6, probably closer to 5. You can do a KH test, but the guess on that is very easy, you KH is 0.0 distilled water IME is usually aroun 6.6-6.8 so the distilled water will not be nearly as acidic as what you have in the tank. Furthermore you are keeping livebearers which really do prefer harder water. Normal soft water wouldn't bother them, but water devoid of any dissolved solids whotsoever with a very low Ph is apt to bother most fish. Unless your Ph from the tap is 9.0 I would quit using distilled water altogether. If there really is some reason your tap water can't be used full strength then follow the advice to mix it.
Dave
 
Thanks. I use distilled for my salt tanks, and thought it would be good for the freshwater tanks as well. I hope I haven't put the other tanks, including the salt tanks, at risk! I will do more of a mixture in the future.
 
Your freshwater tanks are almost always fine with normal tap with dechlorinator. You saltwater tanks should be great with distilled, because the salt mix gives it everything you need. You can also buy specific nutrients that you may need for corals and such. You salt mix adds enormous amounts of buffer (alkalinity or KH) which in turn makes the pH raise to good saltwater pH (I believe somewhere around 8 pH....but I'm not a salty dog, yet!)

I will say that now that you have been using only distilled water for so long, you can't just do a huge water change with just tap water. Either dilute 50/50 tap/distilled and do 25% up to maybe 40% water change, or do very small 10% (up to maybe 20%) water changes with straight dechlorinated tap water. Do these small water changes at least once a week until you get things back up to a decent pH.

I also want to tell you that there are 2 things you MUST buy before getting started with this process: pH test kit and dechlorinator. You don't want the pH to skyrocket upwards too quickly, so check with the pH kit that it is raising no more than 0.5 degrees (which is pretty extreme anyways, IMO), but is better to move up in 0.2 degree increments. It will want to adjust very quickly upwards, I'm betting once you start adding tap, so just keep an eye on things. You don't want the same thing to happen to your fish because the pH and hardness are jumping up too quickly, do you? Ask any questions you need answers to before you make mistakes. Better safe than sorry! :help:
 
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