[APD] "Grainy" or "sandy" water??

["Laith Arif" <laith at swissonline_ch>]

Hello everyone... 

I have been noticing for the past month or so that my water seems to be
grainy or sandy. And recently it has gotten worse. The water looks a bit
cloudy white but when you look closely you can see what looks like fine
particles suspended in the water. It's worse when you look "end-on" then it
looks almost like a sandstorm in there... 

My water parameters are all fine. 200l tank, heavily planted, CO2 injection,
125W of light, 29C, pH=6.6, KH=3, PO4=0-0.25, NH3=0, NO2=0 and NO3=10. I do
a 35% water change every two weeks with a mix of RO and tap water to get KH
down to 3. 

About a month ago I added 4 discus to the tank. Since then I have fed the
fish a couple of times with frozen beefheart and bloodworms (they love the
bloodworms!). Otherwise I just feed flakes and granular discus food. I have
increased the number of times I feed them to 2 or 3 times a day (before the
discus I fed once a day). 

The only other incident is that I have been suspecting my pH controller
probe to be defective because at each calibration (monthly) it was having to
adjust by between 0.2 and 0.3 pH. Also when I measured pH with a liquid test
it was showing me an aquarium pH quite a bit higher than the pH controller
was (6.9 vs 6.6). I took the probe back to the store and they gave me a new
one to replace it and now the pH is where I want it to be and matches liquid
pH tests. 

The above means that for several months now my aquarium was getting about
half the CO2 it should have been getting while I was still dosing
fertilizers normally as if the CO2 level was good. 

I put some "ultrafine" mesh pads in the filter two days ago to see if this
would help and I see no difference. 

I've been thinking that the "dust" in my aquarium could be: 

- excess ferts precipitating out of solution because the plants didn't have
enough CO2 to use them all? 

- Related to the increased feeding frequency (even though each feeding is
less)? 

- My substrate is 4cm of Dennerle Deponit covered by 5cm of gravel. Could
the "dust" be from the substrate? 

- Anything else? 


Any ideas? 

Sorry for the length but better that you all have as much info as possible
no? 

Laith


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