You're looking for a fish cave that feels natural—not obviously artificial like plastic decor or coconut shells. Here’s a summary of the best options:
Slate or shale caves glued with aquarium-safe epoxy: You can pre-build them outside the tank to avoid collapse. They look natural, are safe for fish, and easy to clean.
Handmade unglazed ceramic caves: Especially those with a stone-like or driftwood texture. Many are available on Etsy and blend well with planted or natural-style tanks.
Large driftwood with hidden hollows or combined with stone: Offers both aesthetics and shelter, ideal for plecos, dwarf cichlids, or shy fish.
As for magnetic caves, your concerns are valid—the external piece is often visible and awkward, making them better for breeding than display. Shrimp shelters and under-sand tunnels tend to collect debris and are hard to clean, so they’re not ideal for most setups.
You can hide shelters too. This is from a shrimp tank I'm working on.
Those stacked slate rock on the left. There's a gap between that and the tank wall that shrimps can hide in. There are also some shrimp tubes on the right that are obscured by plants and wood.
