In addition to slowing down and letting your tank go through a full cycle, I'd also try to bring your temp down a few degrees. 81 is on the high side. Speaking from personal experience, I've found it very hard to regulate temp in my 10g and even a few degrees variation over the course of a day can really wreck havoc in a tiny tank. Not sure how much of a swing you are seeing through the course of the day, but I'd aim to bring the temp down to 78 and try to hold it there. And better to do that now while you are cycling than after you've got livestock in.