I've decided for my D. leucomelas viv, I'm going to use a 20 long tank rather than a verticle as I've read they need more bottom space than verticle space. Here are my questions:

1. If I have a glass top cut to fit the tank, will I need any space at all to put mesh for some veintilation or would it be ok to cover the entire top with glass?
2. How will having a glass top effect the lighting I need for the plants
3. (not glass related) If I use hydroton then a screen of some sort and then the ABG, will I still need to install an area of some sort to syphon out water from the bottom?
4. How thick/thin should the top be that I have cut?