Is this something you add to soil or does it replace the soil? Thinking of it for raised garden beds.

This Coco potting soil is extracted from coconut pith. This is the spongy organic material that binds together the long strands of fiber around the coconut shell. We maintain high quality standards in order meet our customer expectations by sifting to remove long strand fibers and other impurities. It is washed to be almost ph neutral to grow ANY plant and then dried and compressed. No chemicals or fertilizers are added since different plants need different nutrients. The fibrous organic material allows absorbs and readily supplies water, nutrients and air. Since this is an Organic growing medium, they enable great growth of plant and its roots. Please add compost (if you are going to do Organic gardening) or appropriate fertilizer recommended for your plants or both. Optimum watering, adequate sunlight and required fertilizer / nutrient will ensure thriving plants!! Happy growing. Enroot Products LLC.

Can the brick be broken and pieces soaked for new rootings? I can't possibly use 2 gallons.

Yes, you could saw it in pieces but it would be messy, I think. It really isn’t necessary to use it all right after wetting. It will remain fine to use in the future although it will slowly dry out again in your bucket or whatever you use for the soaking process. It is just damp coconut fiber. BTW, you will need more water than the instructions say. It is really lovely stuff to use!

Would this be good for pet land snails? Or would it be too acidic?

Not sure I used it for my red wigglers worms and I haven’t had any problems. The worms seem to like it.

Would this be okay in a terrarium? Pesticide/chemical free? How well does it hold moisture? And does it need to be double rinsed/washed?

Yes, It will be okay for Terrarium, a number of our customers have reported that they are using our coir for terrarium. Our Coir is the pith extracted from dried coconut husks and have been washed with RO water multiple times to remove any naturally found salt in the coir and then dried, sifted and compressed for packing. Coconut Coir is like sponge and will absorbs plenty of water. Our high-grade coconut coir is low EC (Less than . 8) and has an optimum pH levels of around 5. 8 to 6. 8, If your pets are highly sensitive to even low levels of salt, you may want to wash it and dry it before spreading it in terrarium. Hope this helps.