and how do I get rid of it please?

what is it, are they alive? or from the food you feed

I don't know, only seems to accumulate in one corner - some sort of fungus?

Is it growing on the glass? Does it move? Is it fluffy? :dunno:

It is not excess food gone mouldy is it?

It's only in that corner of the tank, and only that tank so is not excess food. It's starts in the corner and creeps up the glass if not cleaned out.

Yes, it's fluffyish. That corner gets the most sun so might be some sort of algae? :dunno:

i get debris build up on the glass in the corner diagonally away from the filter where stuff blown around in the current comes to rest. Mine isn't white and fluffy though

Interesting. I would suspect some sort of debris (but I have no idea what if it isn't food) gets blown there by the filter then grows fluffy as it ages.