Fuge hand on setup for chaeto

[4clownfish]

**Title**
Fuge HANG on setup for chaeto
I'm currently using a aquaclear 30 with a modified back. It is now holding about two times as much water. The problem is there is not enough room for the Chaeto to grow and plus my light is longer then the AC unit.
Thoughts
1. Buy a AC 70 and modifiy it (big size difference?)
2. Buy 1/8 acrylic and modify the AC30 more
3. Buy a AC70 case and use the AC30 pump(does it fit??!?)
I want to keep a 50-75$ budget. So I can afford a H.O. fuge thats way over priced and then deal with pumps.
Does anyone have any experience in Fuge's?
My "bio-load" is high for my tank. It's only 20 gallons but the nitrates can flare up quickly. I recently put new LR in, so it is currently cycling. While this is happening I want to work on my Fuge for Chaetomorpha.

 

[4clownfish]

Here is a picture of my Fuge as of now.

As you can see it is small. Caulked like no other, and something needs to be done.
Suggestions on a inexpensive way to make a fuge?

 

[florida joe]

I would forget the outside the tank refug and go with an inside type. You can get a 12X6X8 inch high for $60 and it comes with a designated power head