It depends which plants you have got - some have more specific requirements than others. Can you tell us the names of your plants or alternatively show us a photo and we'll be able to tell you more?
Are you using any ferts or CO2? There's only a few varieties that can tolerate just being left in tank water with no extra gas and ferts. I add co2 and ferts and Tropica plants and plants grown submerged still dye.
