scale or other crud in substrate?

Hi.

I have a 20 gallon that I set up to use as a quarantine tank / water
source for water changes in my 75 gallon.

I hastily set it up and moved a sick gourami into it with only about 5
gallons of water, a heater, a thin layer of river stones, and an airstone
to move the water. I added a healthy dose of aquari-sol to treat the
gourami, but he didn't survive the night. After I removed the gourami, I
filled the tank (with de-chlor) and put an aquaclear mini on back with
media from my 75 gallon. I've also added two clippings from the najas in
my 75 gallon.

Just the other day, I noticed that there appeared to be some kind of scale
or other flaky white stuff covering the river stones. I tried to gravel
vac it up just now, but it appears to be stuck pretty good.

Oh yeah -- I just realized that the filter media I put in to the aquaclear
is ceramic rings. Maybe this has something to do with the crud in the
substrate?

So... any ideas what this is? Did the aquarisol precipitate out? Is it
hard water scale? I haven't tested the water in the 20 gallon, but it is
a mix of RO water and my tap, which comes out to be reasonably hard --
about 8-10 dKH / 12-15 dGH. The thing is, I use the same water mix in my
75 gallon, and never noticed this before (although I use a different
substrate, so maybe that made a difference)? I just did a 33% water
change, and it stirred up some of the stuff into the water column, but
there's still a lot in the substrate.

The only other thing I can think of is that I added a few freeze dried
brine shrimp to the 20 when the sick gourami was in there, I hoped he
would eat something.

I'd like to use the water in the 20 gallon to add to my 75 gallon -- it's
due for a water change tomorrow. Is it safe? Or is the scale/crud
something I should worry about?

Any help appreciated.

--chris





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