They've got hearty appetites and growing fast, it seems like they add 1 mm of length every couple days. This batch has about 30 clowns about 15 mm each, I have yet to transfer them to a growout tank, so they are still in their 2.5 gallon larval rearing tank.
Yesterday a few hours before I was about to head out of town (naturally), I noticed many of them were breathing rapidly. pH was around 7.5. No detectable ammonia but somewhere between 0 to 0.25 ppm nitrite. I immediately put in a bigger air pump and increased aeration to the sponge filter and a separate wooden airstone, and pH gradually increased to 8, and the juvies' breathing returned to normal. IIRC, nitrite toxicity is positively correlated with pH, whereas ammonia toxicity is inversely correlated. So with equal levels ammonia and nitrite, at a higher pH the ammonia is more toxic, and at a lower pH nitrite is more toxic.
I typically keep low fish stocking densities in reef and planted tanks, and haven't really had to deal with the nitrogen cycle or be concerned about sufficient aeration for many years - this was a good refresher.