White fungal problem

[Redbulldog]

It has only been 3 days since I set up my terrarium, but I already have some fungus growing on my branch.

I bought the branch at the same pet shop as all of my equipment, and the guy is a real reptile specialist so I assumed that the branch would be OK to use without any pre-treatment.

I am keeping the coconut fibre substrate moist to achieve the 50%-75% humidity needed for my 2 Gargoyle Geckos, but this appears to be having a detrimental affect on the branch.

A friend has suggested that because the Gargoyle Geckos are happy at room temperature, the fact that I have no heat mats means that the moisture is not evaporating enough and causing the damp problem. The daytime temperature in my terrarium is about 22c/72f.

I am very surprised to see fungus in such a short time and naturally I want rid of it as soon as possible as I'm not happy with the Geckos being in a mouldy environment.

Is there a treatment I can apply to the branch to prevent the mould growth and do I need to increase the temperature?

Thanks guys.