Is there anyway to make a natural looking cave for a larger fish.
The fish is probaly around 30cm so the cave would have to large.
I'm also looking to make some smaller caves for my 20 - 26cm Synodontis Catfish.
I used a plastic container and drenched it with silicon and smeared gravel on the surfaces, but cut one side of it off so it could be dug into to substrate.
Work well for my old tank, and looked very good and natural.
I use big river rocks and build the caves when I set up the tank, three chunky ones with a big flat one on top. I often combine two or more if I need even bigger caves. If you are worried about it shifting put a rock on top.