Tank Disaster, Peat and Limestone

Subject: Tank disaster
>  I hope somebody can help me figure out what's going on with my 
> what is to be done.
snip long narrative>

> So, why is it happening and what should I do now ? Replace the g
> though this would be a torture; wait until the tank stabilizizes
> compensate the daily drop in KH with sodium bicarbonate to speed
> the buffering ?  And ,if I wait, does anybody know how long it m
> take until the tank is stable ?

I agree with you that the most likely culprit is HCl left in the 
gravel.  Too much CO2 would lower the pH but not the KH, too 
little CO2 (and too much light) would lower the KH but RAISE the 

I am a strong advocate of the "do water changes and wait it out" 
approach to instability problems in planted tanks.  It looks to me 
like you are already past the worst.  I would _not_ add anything 
to raise the KH until you reach a stable KH in the tank.  As long 
as you have 10-15 mg/l CO2, your plants will not reduce the KH.  
If your tap water has an adequate KH, your tank will eventually 
recover to match it as long as you keep doing your water changes. 

Subject: Peat substrate and Lime Containing Rocks
> I'm in the final phases of testing various substrate material an
> decorations before setting up a 135gal tank.  The peat and clay 
> substrate cause the pH to lower.  Rocks I would like to use caus
> increase and most importantly buffer my tank - KH w/o rock is 2,
> is 3.  The peat/soil test tank is not dropping the pH as much as
> the beginning of the test. 

> My concern is that the peat will stop lowering pH long before > 
the rock stops increasing it.

I suspect you are right, but rocks are easier to remove than peat 
;-)  My question is why use either?

I use peat in the substrate of one small tank specifically to 
reduce KH and pH.  The tank doesn't have substrate heating, but 
still, after 9 months, the peat is doing its job on my moderately 
hard water.


Karen Randall
Aquatic Gardeners Assoc.
Boston, MA