Hi Ke,
To answer your question, it depends: When a male is trapping a female, I'll skip a water change for a day or more. But I have done water changes while males were fanning eggs several times.
In fact, I'm in the "no water change" situation right now. Saturday I was going to do a water change in the tank with my L397. I currently have one male fanning eggs, so I was going to do the water change. But I noticed my
courting - a male and female going into/out of a cave that day, so I didn't do a water change. The water in that tank was already overdue for a change (it had been 2 weeks since the last water change), but I skipped the water change Saturday and again Sunday because of the courting mustard spots.
I am nervous to let the water get so yucky (@nabulus, you've seen how dirty the water is in that tank currently). But then again, I recall my first ever L397 spawn occurred after a period of tank neglect, and I only discovered the dad on wrigglers AFTER I did the water change (the water was so filled with tannins, poop and food sediments that I couldn't see into his cave before the water change
). So I'm hopeful this time that maybe the neglect has allowed the mustard spots to spawn.
To be clear, I'm not saying either of these species NEED dirty water to spawn. I've had multiple spawns from my L397 in clean water since that first spawn in dirty water. Rather, I suspect that the lack of attention which occurs to result in a neglected tank might provide the hesitant fish extended privacy to encourage them to spawn the first time. Once they figure out how much fun spawning is, then they seem to do it more and more, regardless of how much I bother them with water changes.
That's really all speculation on my part - just a theory - but it's a pretty safe theory.
Cheers, Eric