Disappearing acts

I have a 12gal eclipse filled with lava rock, sand, driftwood, and plants. It also has pothos house plants emersed in the water. It looks really nice. I just added some danios as sort of dither for blue rams. I bought five. They seemed to be doing fine about an hour after being let into the tank. I did however worry about one of the fish because of how the lfs clerk hit the danio into the wall trying to catch him.

Anyway I come home from work and notice that I can't find one of the danios. I fed the fish hoping to see him come out of one of the caves...nope. Next day 3 danios. So I'm guessing that maybe two of them are spawning in one of the caves? But the water smells great, I have two filters in it, the eclipse and a fluval submersible sponge filter. The water is as clear as can be and the other danios are looking great. They love the aquascape.

Should I disrupt the aquascape to look for the danios? Or do you think they are just spawning? I'll take a picture of the tank now...

Thanks.

Nope, they didn't jump out of the tank. I looked around the tank and it doesn't really have any where for them to jump out. I assume they have died in the caves. I'll check after I get home from work.

I tore apart my tank to find that they died. They were under rocks in the sand bed. I will test my water today. For the future should I just let the bodies erode instead of completely tearding apart my rock structure and plants?

I got my water tested at the lfs and everything checked out fine except alkalinity was low at around 20. My ph was around 7.2 and 7.6. Is the alkalinity a problem? The lfs made it seem like it was. How can I raise it. I do water changes weekly, 20%. This is the second time they said it was low.

My water is too warm also. It is around 86 degrees, but could that lead to death? I read that most fish do better in higher temps and it is harder for ich, etc to spread.

Ok, thanks. What about the alkalinity and ph?