A modest performance by the males, and they've "scored" 50%! See if you can spot the fertilised ones in this photo:
I filled a spare 4k litre vat over night in preparation for further water changes. This morning, I added declorinator and some airstones to it, and left it for the day bubbling away. By the end of the day it reached 17 C, which was just close enough to the spawning vat temperature for me to feel comfortable with a partial water change. The spawning vat is at 20 C. I'd like the temps to be more closely matched for the water change, and I went ahead with a partial water change keeping an eye on the spawning vat temp and stopped when it dropped by 1 C. Got a reasonable water change in, probably around 25-50%.
I have 3 airstones in the spawning vat, spread around the vat. I turned down the aeration rate so each air stone is producing just a small flow so that the rising bubbles are just breaking the surface. The idea is to keep a flow, but keep it to a slow flow to avoid causing problems for hatching fry. They are very delicate!
They will probably hatch in the next 48 hours, and a couple of days later and we might see some signs of hatchlings.