I had hydra problems.. until I got the lace/pearl gouramis (T. Leeri).
now the hydras are gone

I had lots of brown algae (diatom) problems... until I got
otocincluses. now I don't get brown algaes anymore

I had thread algae problems.. until I got SAEs (c. siamensis). now the
thread algaes are gone

I had massive snail infestations, picking out 20+ snails from the tank
everyday and still brewing more... until I got zebra loaches (b.
striata). now all I find are empty snail shells

and what do I have in my tank now? 4 SAE, 4 gouramis, 4 zebra loaches,
few otos, and bunch of chain loaches. hmmm... it started out as 12
danio tank! all of them has since died off over the past 4 years...
and the fish I got as my tank cleaners have outlived them...

typical case of tank maintenance necessity dictating what fish to keep!

linda