Whats growing on my platicplants

Question
I just cleaned out my fish tank yesterday. I noticed today that there is this Blueish-Grey stuff growing on the plastic plants. My fish are not acting right.. They refuse to eat..  What is this stuff and what is it doing to the fish?

Answer
Hi Sara;

It sounds like decaying excess food or a type of algae. The fish may be stressed from having their tank cleaned out. If you changed more than 25% of the water, it can shock them. Your tank needs a weekly water change of 25% and gravel vacuuming to keep the water chemistry consistent. If you wait a long time and then do a large change, the fish can go into shock and get sick. The new water can be very different from the old water if it's been in there a long time without partial changes regularly.

If you could tell me a bit more about your tank and fish I can help you further;

How big is the tank?
How long has it been set up?
When and how much was the last water change?
How many fish? What types and how big are they?
How much water did you replace when you cleaned it out yesterday?
Did you use a water conditioner in the fresh water?
Was the new water the same temperature as the old?
What kind of filtration?
Was the filter cleaned at the same time?

Let me know and we can work on this some more if you want to...

At Your Service;
Chris Robbins