I want to talk about substrate/soil.  It is certainly one of the most heated topics in poison frog and naturalistic vivarium communities.  I get asked all of the time what the best substrate/soil is for terraria and vivaria.  Like many things in life, there’s not one simple, one-size-fits-all answer to this very important question, so I want to discuss why some substrates are better than others.

There needs to be some defining factors of different substrates/soils that make them more suitable than others.  In general, a good substrate/soil mix should be well draining, but it does need to be somewhat hydrophilic.  Let’s discuss all of the substrates that I combine together to make, what I believe, is the ideal substrate/soil for most terraria and vivaria.  I’ve tried countless combinations over the years, and I believe I’ve settled on one that consistently works.  With that said, many folks are ditching any sort of substrate and opting for a sponge filter mat in place of a drainage layer and substrate.  It works.  There are several prominent froggers who only use this particular method with great success since so many of the plants we use in our enclosures are epiphytic or hemi-epiphytic.  We’ll leave that for another discussion.  For now, let’s talk about the ingredients for a great vivarium substrate.

I absolutely love orchid (fir) bark.  I mention it first because I firmly believe that it is the most important component of a great vivarium substrate/soil mix.  Why?  Well, dear reader, orchid bark has so many attributes that make it the perfect addition to any tropical soil mix.  Orchid bark is chunky, retains water fairly well, and helps keep any substrate/soil mix light and airy.  That’s what you want!  When soil mixes get too compact, the soil can quickly become anaerobic and starve the roots of the precious oxygen they need to grow and flourish.  It’s a great base for any substrate, and I like to do 1-2 parts orchid bark.

Next, let’s keep it light, airy, and chunky by adding 1 part horticultural charcoal.  Some companies make their charcoal a little too fine for our needs.  I LOVE ferti•lome® charcoal.  The pieces are the perfect size for a good tropical substrate/soil mix.  Adding horticultural charcoal allows oxygen to be redistributed to the soil, allowing for plant roots to thrive.  So, we have 1-2 parts orchid bark, and 1 part charcoal.

Milled sphagnum moss is my next ingredient.  I use about 1 part milled sphagnum in my tropical soil mix.  It is widely used as a soil amendment because it improves soil structure, increases moisture retention, and helps maintain acidic soil.

Here’s where I’m going to give you a couple of options.  We all owe Atlanta Botanical Gardens for creating the ABG soil mix, which this is quite similar to it.  So far, we have 1-2 parts orchid bark, 1 part charcoal, 1 part milled sphagnum moss, and now we’re going to add 1 part peat moss and/or 1 part tree fern fiber.  I’ve had issues finding a consistently reliable tree fern fiber source in bulk, which means I typically use peat moss instead of tree fern fiber.  Either or both work fine.

I have to talk about coconut fiber.  This is going to be an unpopular opinion, but I do not like coconut fiber or chips.  I love that it’s a renewable resource, but I hate that the runoff water from cleaning the coconut fiber may contain levels of sodium, potassium, and physical contaminants.  Hey, if you’re willing to thoroughly clean it in freshwater to wash off all of the potential contaminants, go for it.  Until I can find a good, clean source, I’m going to steer clear of it.

Finally, I want to talk about a couple of optional additives that can be used to add to your tropical substrate/soil mix.  I like to add about 1/2 a part of aquarium soil like Fluval Stratum or UNS Controsoil.  Aquarium soil contains essential nutrients that support plant growth.  Although certainly not necessary, you can add worm castings to your soil mix as well.  Quite frankly, the list is limitless, but the main substrates I mentioned mixed together make an ideal tropical soil mix.