DIY is the fun part!
It's not too difficult to do. Another member PMd me for the instructions but I think I'll post them here too for those that are interested in making them.
1) The hardest step. Cut a coconut in half. This is easier said than done. We used a dremel tool with a cutting disk. A hack saw will work but takes a LONG time. The dremel tool takes a while too but is the fastest method we have used.
2) Drain coconut juice and spoon out all of the coconut. ALL of it. This takes a while too because you have to ensure ALL of the coconut is out otherwise it will rot in your tank. The inside of the shell should be even in color and medium to light brown. The fresher the coconut, the easier it is to get the meat out.
3) Using the dremel tool or saw, cut an opening or two (or 3 or 4) on the sides so the fish can get in and out. The size of the hole will depend on the fish and purpose. We have a few in the 150 Cichlid tank for the fry. The holes are smaller so the fry can get in and out but the adults can't get to them.
4) Drill a hole on the top in the back. This will make sure it stays submerged.
5) Clean it in the sink with hot water.
6) Insert in tank.
I'd say it took me about an hour or so from start to finish. It's a fun project and the fish LOVE it. Good luck! And once you get it done, post pics.