Rust and pH

[Woody]

Last week I posted a message in the Beginner's Question form asking about potential side effects of rust that is forming on rocks in both my aquariums. Most responses suggested that I was seeing algae—not rust. I was already sure it was rust, but nobody seemed alarmed and I decided not to worry about it.

I spent the weekend trying to bring my pH to normal levels after it tested at 7.8 and an angelfish died. After partial water changes and lots of "PH Down" fluid, I have one tank down to 7.6. My wife raised the question of rust again, and I think she's on to something. The following link is to a page that contains enough mathematical formulas to make my head spin, but seems to indicate that the pH level of water affects how quickly metals rusts and, conversely, the oxidation process raises the pH of water. ( http/antoine.frostburg.edu/chem/senese/1...ron-rusts.shtml )

I went home at lunch time today, removed the rocks from my 15-gallon tank and added more "PH Down." I'll be checking the levels again in a few hours, but if anyone has any knowledge of the relationship between rust and water, I'd appreciate any additional input.

 

[Aulonochromis]

What type of rock is it? If its anything calcareous you shouldnt use it with angelfish. It's odd for a rock to rust now. I mean it's probably close to a million years old and it's just starting to rust now? I would not use any Ph down chemicals, instead I would use driftwood and possibly peat to lower the Ph naturally. Some of those Ph adjusters contain phosphate and will give you a serious algae problem. I prefer the "organic" solution to fishkeeping whenever possible.

 

[Woody]

Strangely enough, yes, the rocks are rusting. I found a bunch of plate-size "flakes" at the bottom of an exposed rock face that was cut away in recent years for a highway project. They appear to contain a lot of iron, or some other metal. All chemical attempts to lower the pH failed until tonight after I removed all the rocks. I think there was some immediate reaction going on between the oxidized material and the PH Down. At least, that's all I can come up with.

Unfortunately, the only thing I could find this evening was a phosphate powder. It brought the pH to 6.8. I'll watch for an alge problem and try to use more natural methods in the future. I had never heard of using peat until I started reading these forums. Is it something I should be able to buy in my lfs?

Time to find a new hiding structure for my pleco.

 

[Aulonochromis]

Don't use those rocks if they contain alot of iron. Generally metals are more toxic to fish at lower Ph levels. You can get peat plates at your LFS or even a garden center, but make sure they are not treated with any chemicals or they may harm your fish.

 

[Woody]

Don't worry, those rocks are history. I now have a huge bucketful of stone in my garage if anyone wants to landscape a flower bed or something. I've used natural rock many times before, but never encountered this type. Too bad I drove 30 miles looking for some exposed rock and then made several trips across a snowbank to ferry it to the car in the cold wind a couple of months ago.

Thanks for your advice. And if you need any rocks ...