I appear to have limescale on the back of the inside of the tank, around where the heater wire and air stone tubing go in through...only, there's quite a bit of brown/black stuff. I removed some today, it doesn't appear hard to remove, but a small amount broke off and dissolved in the aquarium water (this was right at the end of my water change...). Of course, there is also some brown/black residue on the heater wire above where the water level is at, and on the air stone tubing.
Is this all limescale, or some bacterial growth? Will my fish be poisoned/catch something nasty by some of it going into the tank? I'm hesitant to remove any more in case I get it into the tank, plus I'm a bit lazy at times and it's been there for quite a while on the glass, the heater wiring and air stone tubing and doesn't appear to have had any detrimental effects. It built up over a short while on the air stone tubing as I replaced it a couple of months ago.
EDIT: Pictures attached, and the left wire is actually black in colour, that isn't the buildup. If the pictures aren't good enough, I'm charging my camera up and can take another attempt at taking photos later.
Is this all limescale, or some bacterial growth? Will my fish be poisoned/catch something nasty by some of it going into the tank? I'm hesitant to remove any more in case I get it into the tank, plus I'm a bit lazy at times and it's been there for quite a while on the glass, the heater wiring and air stone tubing and doesn't appear to have had any detrimental effects. It built up over a short while on the air stone tubing as I replaced it a couple of months ago.
EDIT: Pictures attached, and the left wire is actually black in colour, that isn't the buildup. If the pictures aren't good enough, I'm charging my camera up and can take another attempt at taking photos later.
