Wondering if anyone can identify what this is / these are:
* On the RHS is some snail food - it comes in a pellet which I drop in at lunchtime and which softens and spreads out - it has already developed a fungus-type covering on it which happens if it hasn't been touched. I remove leftovers the following morning. Often, however, it leaves the sand where it was an odd, slightly black colour - although, when siphoning that out, it doesn't actually look like there's anything untoward.
* To its left is what looks like some sort of white mould - it could very possibly be snail poo as he likes spending time on the filter just above the terracotta pot - and it's possible that the snail poo and become covered in white mould.
* Round the base of the terracotta pot is something very black / almost midnight-blue in colour and possibly mouldy too - no idea what that is, and it's certainly much darker/blacker than the aforementioned comment about darkened sand where snail food has been.
I'll do a bit of googling and see what I come up with but, in the interim, if would be good to know if anyone recognises / has experience of them and whether I have any cause for concern re the latter two?