Tacki Cacti

So, I bought these tacky guys:

Yeeeup, "Moon" cacti. Grafted abominations. But I have a good reason! Look at the boring guy underneath the gaudy one. See him? The one with the chlorophyll? He's a Hylocereus undatus, or DRAGONFRUIT PLANT. Did you know those grew on cacti? Did you know about them at all? Look at this crazy thing!

Source: here

Now I don't expect to get any fruit from them (if they live to that point), but I do expect, eventually, for the precursor to fruit. F-L-O-W-E-R-S. And what flowers they have!

Source: here

The flowers only open at night and last a few hours. I hear they're pleasantly fragrant. Oh, and did I mention this is a tropical, semi-epiphytic cacti? The easiest. Like a Christmas (Or Thanksgiving) cactus. If you don't have experience with those, WHY NOT? THEY'RE SO PRETTY! and basically, they're easy plants resistant to disease and tough to overwater and underwater.

So how do you get this plant, without the tacky and parasitic Gymnocalycium at the top? Patience, like this person:

So I'm just going to be patient and fight the urge to pluck the tacky graft off. Maybe one day, when I am old as heck, I'll see my beloved cacti bloom. 

What happened?

I loved you so much, Supertunia Bordeaux. What did I do wrong?

How did you go from this:

To this:

It wasn't the temperature or lack of sunlight. I gave you water and fertilizer, but you still felt weak and wilted. I checked for root rot, but you seemed fine. I noticed that other locals had this problem with your cousins. I cut you back, and you're producing a few blooms, but nothing like before. Oh well. It was fun while it lasted, Bordeaux.