Stella Maris

Jan 28, 2017
So I obviously have a problem with "wetting" the substrate in my sling's enclosures. I admit I over-water because I've had to mold appearing in 3 separate enclosures over a period of 2 weeks. Because of that I completely had to rehouse those slings with new substrate.

My problem is I can't tell "damp" between "wet." Can someone explain this to me?

One of my sling's deli containers has plenty of ventilation holes on the lid and sides, so I'm assuming it's a combination of temperature and moist substrate? He also has a habit of filling his water dish with substrate (burying it). When this happens do I just not bother filling the water dish for some time before he buries it or dumps out the water?

I know organic matter (leftovers, poop)+wetness is a breeding ground for mold. Most of my tiny slings I am able to remove leftovers because I feed them pre-killed large crickets and I take them out 12-24 hours later. But larger slings like my A.seemani and N. carapoensis are shifting their substrate around daily, so I can never find any boli(sic?) left in their enclosures.

I'd appreciate any advice since clearly I am on a learning curve.


Tarantula Guy
Old Timer
Nov 30, 2005
Most will say mold will not harm your tarantula. Once it has used up its food source it all go away. Personally the stuff drives me crazy because I'm allergic.

Where I live I can get it when an enclosure is just damp. Solutions I have found include more ventilation, as a lack of ventilation is a primary cause of mold outbreaks. Removing items that the mold seems to like, otherwise food for mold. In my case I had to get rid of some bamboo chop stix. Plus finding a substrate that works for me, which is dirt and peat.

Damp vs wet? I bet you're more on the wet side of things. Try this, you know dry right? So let it dry out some. Next time you fill the water, let it over flow a bit. Not enough to get the whole enclosure wet. Just the area around the dish. The next time if the area around the dish has dried up, pour a bit in a corner. This way you can better control your moisture levels.

A quick test for wet vs damp. If you move the container, wiggle it and the substrate is shiny or reflective.... It's wet.

If the substrate just got darker but not shiny it's probably damp.
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cold blood

Staff member
Jan 19, 2014
The easiest thing to do is to only dampen half the sub and when it dries, dampen the other side....many people totally overestimate the amount of moisture required.


Jan 28, 2016
Don't try to dampen it all in one go. Till I got the hang of it, I only added a little water at the time. Waited a day then checked it. It'll spread out more than you realize and it's easy to add too much.


Jan 8, 2013
I find it easiest to just give the substrate a few sprays with the spray bottle every two days or so.. The surface substrate remains slightly damp after two days and then I repeat the process.. I do this brcause the surface will dry out faster than the deeper substrate, and I feel that the surface substrate is the one that matters (unless the slings burrow). Also that gives me an excuse to fiddle with my spiders nore often :p


Lady of the mites
Active Member
Mar 25, 2015
You can also add springtails, even to tiny sling enclosures. They'll eat mold and leftover boli.