Actually no way, this would not harm your fish or the fry. It is actually very good and suggested to get your tank set up. The infusoria will be ready and the IAL will do their job while the water ages a bit.
I do this all the time and I found that with aging the water, I get better results. Is also why when you do water changes, the water is aged and covered so nothing can get in. I start to age my water as soon as the pair spawn and put in a few IAL in the buckets that are aging so I have multiple 5 gallon buckets that are already aged and ready to go.
Also just a tip, it's very beneficial to add in just about a cup of the tank water to get the infusoria going in the aging water.
This is very good and I'm glad you actually are doing this. Hope I answered your question.
Originally Posted by AFishTale
I'm a little eager, and have already set up my spawning tank. (My pairs should be here in a few days, but it won't see any action for another week or two.) My question is, setting up this early won't be harmful will it? My setup is a 10g with about 4inches of water, a couple IALs, heater set to 82, thermo, and a bunch of live plants. I figured it would be good to age the water, and let micro organisms start growing in the plants/water. Yes?