Wait at least 4-6 months after tank is cycled to add a nem. Every tank is different, but it usually takes that long for a tank to remain stable month after month.depending on the type of nem you want, I highly recomend getting at least a 4 bulb t5 fixture or go with LEDs. The easiest hosting nem to keep is a bubbletip and they are the most widely accepted nem by almost all clowns. Also, if your only going to have a pair of clowns, try going with something different, like snowflake ocellaris/Picasso perculas, as they aren't the standard everyday Nemo lol. Or maroon clowns as they get much bigger and usually require a dedicated tank anyway as they are aggressive.