I have a few questions?

http://www.3reef.com/forums/algae/algae-scrubber-pics-81850.html

A 20L will make a great refugium but if your going to do a sump/fuge/skimmer I would suggest a 40 breeder

 

Your set up is fine and it seems you are staying on top of the maintence. As long as you have the drip tray over the bio balls, they are one of the best filtration factors going. I would cut down on the feeding and get away from flakes only using them once a week and use more frozen foods.

 

Well this is very interesting as I have been told that the bio-balls are nothing but nitrate factories, and I should remove them. I know 4 or 5 years ago when I was first getting into saltwater they were the greatest things, and I had a lot of luck with my wet/dry filter. But I got out of the hobby for about a year and a half and now I am being told they aren't worth the money they cost and they are more maintenance then they are worth.
I actually built my own wet/dry/sump system that incorperates a drip tray above the bio-balls and got enough of them to do 225 gallon system and it must be working for me as it did before since my system is doing pretty well. I really don't want this to sound like I am not taking advice after asking questions, but I have gotten some mixed opinions, stating that they aren't that good and some that they are great.
I thought I had a problem because my test kit went bad and tested the nitrates through the roof, but a new kit shows my nitrates at about 10ppm, which isn't too bad. I still will be building a fuge, but it will be the only thing in the 20L tank I want to use, as my skimmer is located outside the sump.
Now a question I have is would a couple of powerheads be enough flow in and out of the fuge, like maxi-jet 1200's or similar? I know they are supposed to have a low flow, but am not sure how much. Also how much light will I need to make it successful? I had planned on some live rock, live sand, caulerpa or chaeto algae, is there anything else I should put in, or need to put in?
Any thought on building a algae scrubber filtration system, I found a write up on it and it sounds great, but I was wondering if anyone else has one and if it really is any good?

 

Keep the bio balls. The people who talk against them are "parroting" what they have heard or been told. When questioned, the only negative they state is that detritus gathers on/in them causing nitrate. What they either don't know or care to acknowledge is that the same thing happens with rock rubble used in the place of bio ball, ceramic or any other media. Keeping any media clean negates any possibility of nitrate formation. I have no expertise on the refugium part of your query as I use Halimeda in the display for my nitrate/phosphate user, along with a phosphate reactor.

 

Yep that was my thoughts, just gotta clean the once and a while. I will put the ones I removed back in when I get ready to clean them again.