You can build them a selection of tubes out of pvc, similar to a hamster's tunnels for them to travel through (you would want a bunch of openings of course so water can get through and the fish can play in it, a bunch of stacked 'T' sections - you can epoxy them together instead of linking the pieces), you can make them large enough to fit the fish, and the tubes can even be made of black pvc that way it isn't so garish in the tank. It won't float but it will provide a new toy for them to use. Similar to stacking cichlid stones/rocks (the ones with the hollow insides and multiple holes) but less expensive.
I've thought about that before but I can't really add anything else to the ground because of the Tangerine Lobster. It loves to dig things up and has in a way formed his own tunnels. The lobster and the fish don't mess with each other but the lobster would no doubt take over the pipes and the fish won't be able to use it.You can build them a selection of tubes out of pvc, similar to a hamster's tunnels for them to travel through (you would want a bunch of openings of course so water can get through and the fish can play in it, a bunch of stacked 'T' sections - you can epoxy them together instead of linking the pieces), you can make them large enough to fit the fish, and the tubes can even be made of black pvc that way it isn't so garish in the tank. It won't float but it will provide a new toy for them to use. Similar to stacking cichlid stones/rocks (the ones with the hollow insides and multiple holes) but less expensive.