Just think about adding 2-3 fish to QT per week: treat the old guys, then treat the new and the old, and ... repeat.
Even for schooling fish: school of 3, then school of 7, then 12 - bet stresses them even more. Try that with cardinals, rummynoses, ottos, ...
Courtesy * Integrity * Perseverance * Indominable Spirit * and Self Control
Tenets of TKD