This past Sat afternoon on into early AM Sunday, I got around to changing my substrate to the STS. Figured I'd relate my experience in this same thread for anyone that might be interested. I really like the way this stuff looks!!! Think my fish like it better too. It took a few days but they appear to have gotten over being mad at me for all I put them through.
I'm not at all sure pre-rinsing did any good. Couldn't tell because on the first fill I tripped over the water hose causing it to spray right into the substrate.
What a muddy looking mess that was. About what it looked like the first time I rinsed it. Drained and started over. On the 2nd fill my driftwood, which I tested before I drained the tank, decided to float which stirred up the substrate, moved some of the plants and after getting it back into position and anchored down .. well I ended up with another mess. Since the tank was close to being full I just finished filling and hoped the filter would clear it up. Being the impatient person I am, after 2 hrs and not looking much clearer I said the heck with it. Drained tank again and finally 3rd time was the charm.
I've done some re-arranging of plants which stirs up the substrate and clouds the water a bit but at least it settles back quick and the filter clears the water quickly. Think I'd recommend doing it the way Diana did ... put substrate in tank, add some water, stir, remove muddy water, repeat and then fill. Much easier than trying to pre-rinse it in buckets/containers when using 40lbs of it.
I've had a bit of trouble getting some plants to stay put. My dwarf lily kept wanting to float so put some small stones around it to hold it down. So far, so good. My Sword doesn't have a lot of long roots, so it looks like it wants to float but so far it hasn't. Put a couple stones around it too just in case. A couple plants pop out occasionally but that's probably got more to do with big fish bumping them when chasing each other and not the substrate itself. Plus all plants were previously in too course a gravel which didn't help with growing good roots.
Having to watch my water params kind of close since things didn't quite go as planned. Probably going to end up having a mini-cycle. Tested ammonia today and didn't look quite 0 but not quite .25 either but looked higher than before. Will check it again tomorrow and if needed will do a water change.
Still waiting & watching for the KH to drop. Wondering if pre-soaking might have helped in that regard or maybe it's just too soon. Tested soon after filling and tested again today .. KH still holding at 2-3 degrees. Tap water also tests at 2-3 dkh. My PH dropped from 6.8 to 6.6 but 6.4 is usually what it reads a day or 2 before I do my weekly water change. My tap water tests at 6.4 immediately, then after sitting for 24hrs it's 6.8. GH reads same as always .. tap and tank both at 2 degrees and no change after 4 days. Just got some GH booster and will try to get that up just a bit.
All in all, even though things didn't quite go right it wasn't as bad as I thought it'd be. Planning did help which made it go quicker, even if it didn't go exactly as I'd planned. Now I just hope it won't get too messy when my fish starts nest building. They should be done for the year now so I'll get to enjoy it until next spring.