How long do these morays usually get? Are they all about the same or different (I assume different)? I know you said 30 cm for one of them you currently have.
Also looking another moray (Gymnothorax Polyuranodon) to add. Not sure if I can track them down in NY, USA.
My current morays are as follows:
Echidna Rhodochilus: the smallest is about 30cm, the other two are now about 40cm. This species according to fishbase maxed out at 33cm, so my largest E. Rhodochilus is an anomaly. Either that or I need to re-measure them again
Gymnothorax Polyuranodon: my G. Polyuranodon is around 30-35cm, fishbase said it's 150cm max, but I never personally seen people keeping any G. Polyuranodon over 100cm.
Uropterygius Micropterus: my tidepool moray is around 20-25cm, fishbase said this species is 30cm max.
I personally do not recommend any morays that grows longer than 100cm.
As a side note, Gymnothorax Tile is said to max at 60cm, however as they grow bigger, they also become fiercer.