So yea the subject says it all I plan on changing from gravel to sand and river rock to lava / lace rock. Has anyone ever done such a big change on a new tank? What is the best and easiest way to make the conversion? Obviously I will need to buy the sand and rocks ahead of time but aside from that should i move the fish to a bucket or keep them in the tank ><. So many questions but if anyone can give me some info Id much appreciate. Keep in mind my tank has only been cycled for 1 week if that matters.

I would put the fish in a bucket with tank water. I would also try to keep as much of the tank water as I could.(seeing that it hasn't been cycled but a week) You can leave it in the tank. Try not to remove no more than half of the water. I would try and remove as much of the gravel as I could using a scoop of some sort. You can syphon the smaller particles out with a hose. Don't let your filter dry out and don't clean them during the change. You will need the bacteria in them to stop your tank from going through the cycling process again. You might end up with some cloudy water for a day or two, mostly from the sand but it will clear up. Don't turn them on through this process either. Let the sand settle for a while before turning them back on.
I went through this whole process a while back and everything came through it fine.
Everyone has there own way of doing this but this is what worked for me.
Are you using pool filter sand. It has to be rinsed alot(and I mean alot) but it works better(IMO) than play sand.
I hope this helps. Good luck!!!

I agree with kygrl but what I did was I got a 5 gallon bucket, dumped all of the sand into it, filled the bucket with water and let it over flow until the water was running almost clear. Wile the water was running I stuck my hand into the sand and mixed it up to make sure the water got most of the crud out of the sand.

Personally, and speaking from my own experience put the fish in a bucket. Then drain the entire tank....there is no bacteria that in the water column, most your good bacteria is attached to substrate decor and mostly in the filter and media. Anyway I would then remove your current substrate. You should have the other stuff prepped or ready for prep at this point. Add the new stuff, add water and your dechlorinator and decor...Add fish and turn on filters.

I recently changed three 30s from gravel to sand. I used the black sand for two and, play sand for the other. Cleaning the sand wasn't as bad as I thought it would be. The black sand was actually messier than the play sand for me. I cleaned the sand the same way that Mike mention above. I too Put my fish and the decor in buckets. I was able the to hang my HOB right on the bucket so it could keep running and I tossed an air stone in the bucket with the decor. After removing the gravel and cleaning the tank, I put the sand in, then I put a small plastic plate on top of the sand and slowly filled the tank half way with my python, and a bucket. Keeping the hose right in the middle of the plate and the out flow slow and steady, really helped me keep the sand from mixing with the water. I carfully used a small, fine mesh fish net to scoop the reaining debris from the surface of the water.. I then put my decor back in and arranged it to my liking. After that, I finished filling the tank with the python and bucket, making sure the out flow from the hose stayed even with the top of the water so the sand wasn't disturbed. The water was a bit cloudy at first but it cleared up in about 2 hours. I'm not sure this was the right way but, it worked well for me. Hope this helps you grays. Ed