A heat gun or hair dryer & a way to clamp the piece you're bending. Also a glove so you don't burn your fingers while handling the piece to make the bend. I've seen threads where folks are making cones by putting sheets of acrylic in the oven weighted down in the middle.

I haven't bent any real large pieces, but here's a photo of a small item that I bent a hook on to for hanging on the tank rim. For this all I do is apply heat with the heat gun & once it softens, bend it over the rim & hold it in place with a gloved hand until it cools & hardens back up.

https://tsl4pa.blu.livefilestore.com...31c.JPG?psid=1

I use lexan for a lot of things. Here is sock holder I made for my sump. This is probably the most difficult with multiple bends that are close together.
http://www.canreef.com/vbulletin/sho...921#post859921

Various methods can be used, incl sandwiching lexan between two straight edge pieces of wood in a vise. Or can use a rubber hammer over wood. Easier to make the bend (more leverage) before cutting the end off the lexan piece.

Trick is to use the thinnest lexan material you can find. It is light, has good light transmission, and holds its shape after a bend. It is very similar to forming thin sheets of aluminum and other metals. I learned this from building airplanes. As you know, airplanes have to be strong, but also very light. A straight skin only has strength in tension. But a skin with curves and flanges also has strength in compression. That design allows you to use the lightest materials for a given strength requirement.

Guess I should have been a little more clear on my question. I've bent acrylic and formed it before using heat. So that I'm okay with.. Just wondering what the flange has to do with it and how it looks in the end?

Just get concept to build you 2 lids out of glass with the plastic back for plumbing n the plastic joint for lifting a little part for feeding
It's probably cheeper then you think
The lid for my 90g is 2 lids and was $30

The simple solution to your bent acrylic is to take a small 1" piece of acrylic and mount it across the whole lid in a T to the original piece. This serves two functions...it keeps the original one straight and it gathers any humidity to the center and drips back into tank.

I kind of want to stay clear of glass lids as they're being taken off aswel.