I would like to change my lightly plants community tank to more densely planted, planted tank. i would like to add a layer of special plant substrate under the existing layer of gravel
a) is it possible to do this without moving any of my fish from the tank
how would i go about it?

it would be great if you could help

thanks

Many (if not all?) special substrates (e.g. Tropica, JBL AquaBasis, Tetra) would severely cloud the water if you add them as you are hoping. I 'think' I have seen EcoComplete added to a stocked tank but I am not 100% sure.

You could get some really big buckets, net the fish out, empty as much of the water into the buckets as possible, add new substrate, put fish/water back in. Run the filter (if you can) in the bucket whilst you are doing so. This is how I would look to do it personally, keeping the tank water as best as you can will help aswell as the fish won't have much change.

What I did on my very first planted tank was the following and it worked well. I always run two filters on my tanks. One of the left and one on the right (I left everything running while doing this, I then pulled all my plants and wood etc out of one side of my tank, all the fish naturally ran to the other planted side and I put in a lexan wall dividing the tank ( I have a cnc at work so I custom cut one to size). I then scooped out 90% of the substrate and set down a layer of flourabase replanted and and let my filter on that side clear the water right up, and then pulled the wall, and started yanking the plants and wood etc on other side and put the wall back in and did the same thing on the other side. And once that side was clear I pulled the wall and did a good water change, and that way I was able to leave all my fish in there home and leave my filters running, and i lost not a single fish. They didn't even seem to react much different then when I do a fair size scape change, or heavy pruning.

Thanks for that last reply that sounds like a good plan. thanks!!