thinking of a gravel change

I don't know what would be good for the plants, however, I do know that it will be a pain. While you are doing this, you will probably have to remove your fish so that they are not injured or over stressed. Next, it would probably be easier to lower the water level then remove the old gravel with a dust pan or something simliar. I would leave some of the old gravel though, since it contains a lot of the needed bacteria.

I will warn you that this is a real pain in the butt to do, but it is possible.

read skepticalaquarist site

On skepticalaquarist.com there is a section about setup and a section there about starting over. WetmanNY talks at length about how to redo a tank. In particular, the bacteria in the top 1/2 inch of the tank is full of one bacteria, the lower part has another. You really need to keep that top 1/2" of gravel safe and happy in order to move those bacteria to your new tank. Even keeping them wet and in a stocking to hand in the tank or lay on the new gravel will be good. For the planted tank, you might want to save the mulm for the lower layers of the tank.

I agree, go on and move the fish and the filter if possible to a big bucket or temporary quarters while you do this. Trying to remove gravel with fish in tank will stir up a case of Ich as you scare the fish to death -- been there, done that, don't recommend it.

if you preserve the bacteria and the filter and treat the fish as carefully as possible, move to a dim tank with a cover and filtration and familiar plants and decor, it ought to go smoothly. It will be a chore, but you will be happy in the end. Keep as much of the tank water as you can, just to keep parameters the same.

orthoscopic substrate surgury

I've changed substrate styles in my tank more than once. I started out with crummy green large grained gravel and moved to sand. I just very carefully scooped/pushed the gravel over with a glass top to a small aquarium to make bare 1/4 to 1/3 of the bottom and dropped my sand in a long 1" tube and funnel (old UGF uplift tube). After waiting a few minutes I used an airline hose to suck any sediment I missed while washing the sand kindof like a gravel vacuum. I slowly laid out the contents of the tube in whatever thickness I wanted untill it was empty, and refilled the tube. The fish weren't too stressed about it. I waited a week and did the next 1/4 or 1/3.
I did the exact same procedure with my florabase substrate when I went planted. The airline trick kept the tank from being flooded with red sediment and as long as I took my time and went slow the fish were ok with it. I stopped with 3/4 florabase and 1/4 natural sand because I thought it looked neat.
good luck

I changed mine out while the fish were still in the tank too. As famman said, take it slow and the fish should be fine. I used a peice of aluminum screen folded like a scoop to remove the old gravel and add the new gravel.
There are several plant friendly substrates out there. Flourite along with Flora Base come to mind.