Growth?
They haven't grown that I can measure. We're probably getting a different individual each time I put one under the microscope, so it's hard to be certain. But I'd say most of them are actually between 2mm and 2.5mm. At 60x magnification, the field is 3.5mm wide, so I'm using their size relative to the size of the picture to estimate length.
We think we've seen feeding behavior, but we're not certain. We haven't captured it under the microscope. But to the naked eye, sometimes it looks like they're feeding. When we turn on a bright desk lamp to the side of the tank (only occasionally) the rotifers move towards the light, and the inklings seem to follow.
I'm hoping to borrow some time at a biology lab at a local university in the next few days. Hopefully I'll be able to better observe things on a better microscope.
There's bad news today too. We had substantial deaths in about half of the rearing chambers. In studying the differences between the chambers where they did well and those where many died, I think we've been overfeeding them. We're probably overwhelming them with rotifers that die before they can be eaten. So I've flushed the water in the rearing chambers, re-stocked them with fresh hatchlings, and am now being much more controlled about the feeding. I got a good maginying glass and was able to estimate the density of our rotifer cultures at 80/ml for one and 100/ml for the other. So now I'm using a syringe to draw a calibrated amount of solution from the rotifer culture in an attempt to keep the prey density at 100-200/liter by adding a little bit many times a day.
We also setup a third tank, using a different paradigm. This is a bare 10G tank, filled with about 8G of salt water. There's a heater and an airstone and that's it. We put in about 100 inklings, and am dosing it with "Ultimate", the water conditioner we were sent with the rotifer culture. This de-toxifies ammonia etc. so that you don't need a bio filter.
We're probably got another day of fresh hatchlings before I won't be able to re-stock from any further problems. And I'm not getting any of my work done this week. It's a good thing I'm self-employed (though my clients aren't happy...).
-Mark