Q. How big of water changes should I do?  Water changes are one of the cheapest and best ways to get awesome aquarium plant growth. You’re fish will love you too.  A good way to explain the value of water changes is this. Say you are in a room full of people who are smoking. The room is full of cigarette smoke and you’re gagging. You could rely on a big air filter in the room. I’d rather open up the windows and doors and replace half the air with fresh air. Same deal with planted tanks.  You can make water changes fun too. When I change the water in my planted tanks it’s a very Zen time. I unplug the filter and drain the tank down with my siphon tube. (get a 50 footer and water your plants outside)  While my tank is draining it’s quiet and I look at all of the plants closely. I remove any leaves with spots or that just look bad. I also top some plants and replant them lower. While you are refilling notice how any new growth almost instantly shoots up.