DIY Burrowing Substrate

[mistyskinks]

Does anyone have any recommendations for making your own blend of substrate that will hold tunnels?

I looked at the Excavator Clay substrate commercially sold, but I disliked that the tunnels would harden.

I've read of people adding organic potting soil -- but what organic potting soil? I couldn't find any that didn't include some kind of organic fertilizer, which I assume we'd want to avoid.

I usually use a blend of cypress mulch and coconut husk. Our Bluey can dig, but it doesn't hold the tunnels. I'd like to add a substrate that can hold tunnels for some added fun and stimulation for our Bluey!

[mistyskinks]

Additional Question:

While I'm at it, does anyone know if Zoo Med's ReptiFresh would be good for Blue Tongue Skinks?

[Y33T]

Soil sand mix and pack it down really well should hold tunnels. There’s a lot of mixed opinions with organic soil, but I’ve seen a lot of people use ones with organic fertilisers no problem and that you just need to avoid ones with manure or chemical ferts.
I personally just pile some sugar cane mulch in a corner or in a repurposed cat litter tray for mine to make tunnels into and they seem to enjoy it.