Live rock in freshwater

kamikaze_fish said:
I got a reply from a friend that said he thinks, in fw that it would be an algae haven because the rock is so porous. True?
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i disagree because even though it is porous, not every nook and cranny is exposed to the light, so algae wont be able to grow on every part of the rock. instead, i would think that the porous rock would house more bacteria due to the increased surface area.
 
it would definitely become freshwater bacteria housing, though not to the extent that it would in saltwater. assuming that the fish in the tank will be compatible with the water chemistry the rock will create, the only problem i see is that the little pores and holes in the rock may trap a lot of debris, and your nitrates may be higher than you'd like. but if you just took a powerhead and blew the water at the rocks to clean them out just before you do water changes, that would probably clear that issue up.
 
This weekend I took the plunge and put the rock in. The tank looks great with it in there, but I did however put the fish from that 10g into my 20g just so I can watch the chemistry of the 10 for a while. After 48 hours the ph went from 7.0 to 7.5 but that's the only change I've seen so far.
 
With a pH rise that big I'd want to know the underlying KH and GH changes - far more significant.
 
A PH change of .5 is significant. That means your ph went up 5X higher not 1/2 point. You can google for the math as to how this works out. I no longer remember how to calculate it. That is why what many see as a small increase can stress fish severely. It is not a small leap but rather large.

This may help explain:


It is important to note that the lower the pH number the greater the acidity and also that the difference between a three and a four is that the 3 is ten times more acidic than the four.
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Well I'm very glad I took the fishies out first. I hope to see the numbers settle down quickly. If they do, I'll probably try to get them to adjust to what I want them to be and see if they stay settled. If so then I'll be happy with it. Is it wierd that the water went more alkaline?
 
I failed to include a very important piece of information. I also put a larger filter and new to me (used) submersible heater in the tank when I put the rock in. Additional reasons to why I put the fish in the other tank. Didn't want to chance a mini cycle or some strange change in the water quality giving them problems.
 
It's true that half a point means a 5 fold reduction in the concentration of H+ ions. However, it's wrong that this will affect the fish. It won't. However, associated changes in the Total Dissolved Solids might well. It's almost certainly the case that pH shock doesn't exist; osmotic shock caused by sudden changes in TDS does.
 
I would be a bit concerned with the TDS changes you may experience.

dead (once live) rock will have been exposed to many minerals. KarlTh is referring to.

this may cause a change in KH/GH which may be detrimental for the fishes(depending upon species)
I definitely would expect a rise in KH as calcium had been deposited on live rock over the course it has been exposed.
 
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