calvus so close to breeding

[supafreak]

I have a 55g tank with many calvus, julies, and some tangankika cats. I was really excited the other day when i saw my female hanging out inside a shell. I thought forsure she had spawned.....but nope. She is constantly trying to get the attension of one of my larger males, but he just seems to ignore her. She is camped out at the mouth of her shell, and has been for days, and when he comes close (he's never to far away) she startes to convulse, and moves inside trying to get him to follow, but he won't bite
I'v been feeding frozen brine shrimp everyday, and just don't know what else to do. How long do they go on like this before a successful spawn? this female has spawned before, back in june, but i missed that one.
oh and i also need to do a water change, but i don't want to upset anything (water temp, ph, even scenery) since i think they are sooooo close.

 

[supafreak]

sorry guys, my computer is acting funny, and i think i may have posted this multiple times.....

 

[Menagerie]

I fixed the double post

Go ahead and change the water, but forgo the vacuuming. Only put the siphon at the very top and when you put the water back, do it gently.

Aside from brine shrimp, try mytis shrimp, blood worms, or daphnia. If you can live foods sich as vinegar eels or microworms, they would appreciate it!
I never see my shellies spawn, but there always seem to be a fry or two around.