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Re: Substrate problems

> Date: Wed, 16 Jul 1997 18:44:45 +0800
> From: Roy Cheok <roycheok at cyberway_com.sg>
> Subject: Substrate problems
> But the good new is that I have no measurable ammonia, nitrate reading, 
> nitrite is < 0.1 mg/l, and the water temp is around 30C (86F), and cooled
> in the afternoons by addition of ice blocks. The problem and bad news is 
> I can't seem to get my PH down....and it hovers between 7.0 - 7.5 PH, 
> and I would like to get it down to about 6.5 if possible. I then bought 
> a KH test kit and started keeping tab on this, and it hovers between 
> 7 dKH after a 30% water change to 17dKH inbetween twice monthly water 
> changes. This is without any buffering and I know that my tap supply is
> soft. 
> I then suspected the gravel, and tested it with some vinegar. Wow, immediately
> after addition of vinegar, about 30% of the the gravel started
> (mostly whitish looking pieces amongst the brown pieces) bubbling...and 
> probably the cause of my KH and PH going upwards.

Oops...   :-)

I don't know much about the geology of Singapore, but perhaps the gravel
contains bits of coral or shells.  This will add calcium carbonate and
raise hardness, alkalinity and pH.  It also provides some buffering for
your soft water.  People are often advised to solve problems of soft water
and no buffering by putting a few shells or some crushed coral in their
tank or filter.

> Now the issue is should I tear down the tank and discard the gravel, or 
> should I just continue since it appears to be a natural buffer for KH..and 
> if I perform weekly water changes, I would be able to keep the KH to about 
> 7 or 8 dKH. And, how can I ever get the Ph down to a preferred 6.5, since 
> IMO the gravel would almost certainly cause it to go upwards?. Also, should 
> I start testing for general hardness as well....?

Your tank sounds beautiful, and although your fish may prefer a pH of 6.5
they should do just fine at pH 7-7.5.  It's not really a problem unless you
want to spawn the neons!  

It's really up to you whether you want to tear down and start over again.
More frequent water changes will probably help stabilize things, and if
some theories are correct, your gravel will eventually get coated with
bacteria and other organic material and stop affecting your water
characteristics.  I would be really interested to know whether this happens
in practice.  

Turning off your RUGF should reduce the effect the gravel has on water
characteristics, perhaps considerably.  With an oversized Eheim and all
those healthy plants you probably have plenty of filtration for your
fish load.  You may want to experiment with this.

Please let us know what happens if you stay with the current setup.