YIKES! What are these?!

[FlyingChicken]

On the floor of my 4ft tank, these dirt-like stuff appeared 2 days after I move my fishes out of the tank. What are these residue? It's disgusting...

Picture of entire tank with residue on floor


Close up shot of the "dirt"

[vinz]

Looks like something in your tank precipitated. It can happen when chemicals (from tap or your additives) in the water react to each other or other water properties change like temperature or pH change.

It could even be chemicals (either from tap or your own additives) in the water reacting with something in your filter?

You posted a few days ago that your tank water turned brown and cloudy. Could be the end result of whatever was happening then.

What has happened, or what have you done since your tank water turned bad?

[FlyingChicken]

Because this main tank water had turn "poisonous", I move all my fishes to my old 2ft tank for treatment as well as a place for them to stay temporary. Luckily, only 1 of the fishes cannot survive the ordeal. Their open wounds and ulcers healed after 2 days...

I've not touch the main tank after I migrate my fishes over. To prevent stagnant water, I keep the pump running to moving the water around. I'am going to sterlise the tank when I notice this funny residue in it...it never appear when fishes are in it though...

[vinz]

Did you change water just before the cloudy brown water incident? Do you change water straight from the tap? Did you add anything to the tank like water conditioners, fertilisers, etc (other then the hornwort)?

[FlyingChicken]

I only add aquarium salt and anti-chlorine/chloramine to all my aquariums because the water come straight from the tap...seems ok rite?

[XnSdVd]

Just a stupid comment but,
it looks alot like the white ppt you get from limewater and CO2. in which case it's some kind of carbonate. If you'd like to test take some of the "stuff"(it should feel hard and try if you manage to break it) and drop it in some acid. Regular coca cola(yes, the drink) will do. If you see violent bubbling then it's probably that. In which case your water is quite safe for the fish I think.