mould on toilet roll seed sowing

i have tried the toilet roll idea for the first time to try and get some baby carrots from the poly tunnel as soon as i can. i trying using toilet rolls and also tubes of news paper (mainly as i haven't got enough toilet roll tubes, and have lots of newspaper).

they are stood up in a cat litter try and have been watered from the bottom, not too much that there is standing water though.

i have noticed the last couple of days that they smell and there is mould growing on the outside of the tubes (both types).

is this normal or am i doing something wrong?

White fluffy mould is very common, especially with toilet roll tubes as the glue used to hold them together is good fungus-food. Doesn't seem to do any harm, but best to keep them moist rather than wet.

Don't recall there being any sort of pong associated with it though - what sort of pong is it?

Sounds about right for toilet roll tubes.

Are you sure it's MOULD?