Re: Tank turned from clear to completely milky in <2 hrs

["James Purchase" <jppurchase at rogers_com>]

Shane, how long had the soil based tank in your office been set up and
running before this problem came up? What type of soil did you use and how
was it prepared before it was put in the tank? Properly set up soil tanks
are usually very stable after the first 6 weeks. High levels of ammonia and
nitrite are usually the only things you see during that time as organic
matter in the soil becomes mineralized.

Did you change anything recently that would disturb the substrate? When you
did that 50% water change, did you disturb the substrate?

Is the filter clean and operating properly? Has the biological filter been
knocked out?

Milky white/grey water is usually a sign of bacterial bloom and high levels
of bacteria can cause oxygen depletion but such numbers usually take a bit
longer to develop than you have indicated. Mild bacterial blooms are normal
in newly set up tanks but rare in established ones unless something is
seriously wrong.

Where is the tank located in your office? Could someone else have had access
to it while you were out for coffee or visiting the bathroom or gone to get
some photocopies or dealing with a client?

I would strongly suspect that a third party might have added something to
the tank (maybe innocently, maybe not so innocently). In office situations
it is quite common for everyone to think that "they know best" and to fiddle
where they shouldn't.

I'd perform several 100% water changes (carefully, so as not to disturb the
substrate) to make sure that anything which might have been added to the
tank had been removed by dilution. Let it sit for at least 24 hours after
the last water change to ensure that the cloudiness doesn't return before
you put the fish back.

James Purchase
Toronto