The first picture shows a trio swimming side by side, the males have slightly longer dorsal fins and a more pronounced jaw. The males go either side of the female and 'tickle' her with their anal fins when ready to spawn. She then produces the eggs which are fertilized by a male, the eggs are then gathered into one of the males mouths and hatched in there. The male then doesn't eat until the young have been released. When hatched and free swimming the fry are released to fend for themselves, they usually gather in the spines of one of my urchins.
I'm still running the tank skimmerless using algae as my main nutrient export and the inhabitants are extremely happy. I have noticed a large amount of sponges and tunicates appearing which are obviously appreciating the unskimmed water.
