I'm not familiar with these but I've seen ones that float, ones that come with suction caps that stick to the glass and others that have two metal brackets at the top that you bend over your glass. There may be other styles but I'm not aware of these.
Would you not try to set up a smaller tank for your fry? Can pick up a small tank and equiptment for cheap and its better I think. Can also work as a quarantine tank when the fry are older.

/cgi.ebay.co.uk/NEW-4-pk-x-20mm-Double-Sided-Suction-Cups-Pad-Sucker-/320441355184?pt=LH_DefaultDomain_3&hash=item4a9bcb0bb0#ht_2479wt_905if you push it against the glass it should stay without suction cups![]()