I have just rescued a 70 litre fish tank with about 40 guppies in it.
The water is so brown that you can't see the fish and it smells really bad.
When we picked it up we removed 80% of the water to transport it and replaced it with fresh water. After this 80% water change you can still only see about 5cm into the tank.
It has a gravel substrate which is full of detritus. We haven't gravel siphoned yet for fear of sucking up fish which we can't see due to the brown water.
We have also taken out one dead fish, there could be more dead fish in there which we just can't see.
We havn't done a water test yet, due to the color of the water making it hard to read the color in the test tubes. So we have no idea what the water parameters are. But I'm guessing they are way off the charts.
I'm worried that by changing to much of the water two quickly will stress the fish. These fish have obviously gotten used to very extreme water conditions.
How should I go about recovering this thank without harming the fish.