These are pictures of the parts.
First is a return fixture that I think came with an Intex pump I purchased last year to use with my blue easy set pool (2650 gph). The pool died but I kept the pump and all usable parts. The return is 3" in diameter which fits nicely on the inside set of threads on the fixture that is in the wall of the pool.
Second shows after the center grid was removed. My husband used wire cutters to cut the grid out then a dremel to grind down the nubs. I actually photo-shopped it to depict what it looked like after he was finished.
Third one shows the elbow connector that came with the fountain. The end that is inserted in the return fixture is threaded. Sorry, I had it assembled before I thought about taking pictures and now I'm afraid to take it apart for fear it won't go back together as well. The hose attaches with a hose clamp (I need one that won't rust). The number of sets of holes you cover determine the height of the fountain. This thing came with all kinds of parts but p*** poor instructions so I had to wing it.
I found out the hard way that you should make absolutely sure that ALL kinks are out of the hose. It took me a couple of minutes to do this and the pressure made my filter spring a leak. All fixed up now. I had to open the filter and re-seat the gasket with more lube. But all is okay now.
We love the fountain, it looks and sounds wonderful. My 9 year old granddaughter has decided that the fountain marks the gateway to the wicked witches castle. She has developed a whole, very detailed game around this. And she makes me play it with her. . . gotta love the babies!