It really does look like the gel given the rough shape (as in, not smooth or round). If you still have it, let it dry out and see what happens. The gel crystals will shrink to almost nothing when they dry, but can be re-hydrated again. What goes into the tank and where does it come from? Any store bought crickets, or store bought plants? The gel crystals are sometimes used in plants, but this would be a rarity for most plant sources.