Re: [APD] Water Changes and Crypt Rot

["Richard J. Sexton" <richard at aquaria_net>]

>I have been reading past posts about the desirability of frequent large 
>water changes.  While reading those I also read several posts about 
>crypt rot occurring when big changes in water chemistry are made.  When 
>I had crypts in my old 120 gallon tank, with DIY CO2, but not much of 
>it, my crypts would rot much too often, then most would grow back, but 
>never all of them.  I was changing 15% or so of my water every two 
>weeks when I was having the problems, but I also did not add any KNO3, 
>and only squirted some iron rich fertilizer in with the water changes - 
>no measuring at all. So, my obvious question is, if you do 50% water 
>changes weekly, do you also risk having more crypt rot?  I have given 
>up on crypts due to my past experience, but I really would like to keep 
>growing them in my new tank, when I finally get it set up.

I've yet to see a definitive answer on why crypts melt. I don't think
anybody knows really.

The Dupla book says "high nitrates" bit if by high they mean 200ppm
both Tom Barr and I have not found that to be true.

I can change 50% of the water every day and they don't melt. So that's
not it. I can change 80% of the water all of a sudden after ignoring
the tank for 6 months and that won't do it either.

The only thing I've found that will make them melt 100% of the
time is obtaining crypts from anywhere and putting them in
my tank. They always melt and they always come back.

I have a suspicion that it works like this: the plant grows
some place and makes leaves in a certain kind of water with
a certain chemical makeup. Soft, hard, what have you. The
leaves are "optimized" for lack of a better word for that
water. When they are moved to a different kind of water the
leaves made in the other water won't work well and they melt
and it makes new leaves compatible with this water.

I can move crypts from any of my tanks to any other of
my tanks, disturb the roots what have you and they
won't melt.

As to why your melted, hard to say. Without watching you actually
change water I don't know. Did you perhaps shut off your filter
for a while ? Lights heating up the surface of the water for
any length of time leadomg to thermal stratification is somehting
I've seen make them melt but usually it takes a while.

A large dose of iron all at once might do it - it seems the
most likely exlpanation.

I have routinely made 80% water changes several days in a row with
no problem. I would not hesitate to make water changes of any size.
If however your tank has sat for a long time and the water change you
make causes an abrupt change in water chemistry that would do it.

What temperature is your tank at and what crypts do you have?





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