I recently flushed out my CH system [1] and renewed the inhibitor - 4 litres of Fernox MB1, most of which I poured into a radiator, but also put some in the F&E tank, as suggested on the bottle.
At the same time I made a new (not airtight, but getting on for) lid for the F&E tank out of a piece of perspex. This was about 3 week ago.
Yesterday I noticed some funny stuff floating on the surface of the water. It looks like a cross between mould and frog-spawn. When you remove it, it compresses like wet tissue or cotton wool.
Anyone got any idea what it might be, and of the likely consequences? I've removed this batch, using a tea strainer, but it will probably come back.
[1] In case it's relevant, I didn't use any flushing chemicals but I did take all the rads off and wash them out with a hosepipe, and I flushed the pipes out by opeing each radiator valve in turn (with the rad off!) until the water ran clean. I also flushed the main flow and return loop between boiler and airing cupboard.