I don't believe in skimping on feeding either, especially for growing animals, I'm with you on that. I'm yet to hear of a marine fish dying from obesity, quite the opposite! As long as there is no left over food floating around the tank after each feeding keep doing what you are doing :)
20ppm is not a massive problem but I would keep trying to get it down. 2-3 water changes a week are not bringing your nitrates down which makes me think that as fast as you're removing wastes the tank is replacing them and that sounds like a lot of work!
You've probably been familiarising yourself with the nitrogen cycle or the process that results in nitrates forming. In short, you need to increase your filtration as its not giving you the results you want to have with water quality right now. Its hard to know where to start because there are so many options.
They fit into 3 categories worth researching:
- biological eg. live rock
- chemical eg. activated carbon
- mechanical eg, skimmers
Replacing your skimmer with one you are happy with is something I'd recommend only because its important you are happy with your tank! So if you can then go for it. There are some compact and short skimmer designs that may be suited to a smaller sump. I'm not very helpful with the equipment side I'm afraid. I like Tunze products because they are energy efficient, you can get parts without a drama and quiet.
@NiCd introduced me to the brand, he's a good person to pester with equipment questions :D
Personally, I would suggest a Marine Pure block to increase your bio-filtration - this does the same job as your live rock, just in a smaller, neater package, no electricity required or noise produced and it will last. You could place a block under your skimmer in your sump.
http://www.thetechden.com.au/MarinePure_Big_Block_p/900111.htm
You could also add a bag of Seachem Purigen to the sump.
There is also this product (free postage over $25):
http://www.vitamingrocer.com.au/One-Only-Live-Nitrifying-Bacteria-for-Saltwater-p/306106.htm
You can use it to add a bigger amount of bacteria to your tank to bring the nitrates down. I'm yet to try it myself, have done the research and placed an order.
These are just a few of the many things you could choose or try.
Over your head? Nah
;) Learning about the creatures in the ocean opens up an entirely different world, one we can only visit and its a great escape from stress. It can be as simple or as complicated as you like. You'd be surprised how many of us find this hobby good for our mental health :)
I'm sorry to hear about the loss of your son, I am sure he is never far from your thoughts xx