in very large tanks, and a 100 is just ovver hte size that you should have for a pb(either one), any tang, should have 75 gallons of water for 1, and multiples, need much more room, especially the larger ones,
and that almost makes sense, about the ick, but i have seen many cases, wher they have contracted ick, with lr, so even though it makes sense, i would not want to put any money on the table, you can look through old posts and find lots of references to hippos or otheer tangs, scratching against the lr(most of htese have resulted in ick )
HTH