Is the "sucking loach" an otto?
http://www.fishlore.com/profiles_otocinclus.htm
To put it in perspective for those of us non metric,

I figure your tank is a little over 30 gallon. That's a nice size.

If you
completely complete your
nitrogen cycle before adding any more fish,
keep up your weekly water changes when you do,
allow a couple of weeks between fish additions,
test the nitrAtes to be sure they stay
under 20,
give your tank a while to settle and season a couple of months before adding the neons,
you probably will be ok.
It's not that those are alot of fish, it's just so tempting to add too many fish too soon.
Then you wind up with
ammonia problems, fish death, sadness and frustration.
Take it slow,
alicem
