Well, for the mandarin, you can actually buy the pods online to put in your tank and replenish the popluation--your mandarin will thank you! They don't eat the things that you are wanting to grow--they're reef safe I'm sure. The algae that you got was probably just grazed down by your fish--it's a tasty treat for them!
I live in the sticks myself, and we have well water. I used a water treatment when I filled my tank. It took forever for me to get it all cycled out and the algae to slow down. I can't use an Reverse Osmosis unit, so I buy distilled water at Wal-Mart. Now the only algae I see is a little green that gets on my glass some and on the rocks. The snails and crabs need it to eat on, though, and it doesn't hurt anything.
All of my live rock has come from the LFS. If it comes from the store, you can put it in the tank with your fish if you hurry and get it home. Rock that your order online should always be cured in a separate tank or bin before being added to your main tank. The die-off that happens during shipping could cause a cycle to happen in your tank and maybe hurt your fish. I added several pieces from the store, though, long after the fish were in and nothing bad happened.
As far as ordering online, it's about half and half with me. Of my seven fish, two came from online (but not SWF...I hadn't found them yet when I ordered!) I had a few DOA's in that shipment, so it was a little disappointing. I haven't had much luck with my cleaner shrimp shipping, so both of mine came from the store, but my peppermints came from online. About half of my snails and hermits came from online, and my bubble tip anemone came from online. Only my brain coral and flame tip came from online, the rest from the store, but all of those were fine. You will find that the prices online are cheaper, sometimes by half or more, but you pay shipping, plus a lot of sites require a minimum order, so you have to order several things at once, or else a high ticket item to meet the required amount. You also need to very carefully check out the guarantee policy BEFORE ordering. Not all guaratees are that great.
My tank has been up for 11 months, getting close to the one year mark. I just recently (Monday) switched to sand instead of crushed coral on the bottom. I have seven fish--yellow tang, coral beauty, scooter blenny, three-stripe damsel, 2 percula clowns, and a flasher wrasse. I have two cleaner shrimp, three peppermint shrimp, two emerald crabs, who knows how many hermit crabs and different snails. I have a bubble tip anemone, which is the newest addition to my tank, a brain coral, flame tip, colt, and some purple mushrooms--I'm not sure what they are. I just started collecting the corals, so hopefully I'll have more soon! I almost always have to order the corals online because there isn't a good supplier anywhere near me. There's a store about two hours away that sometimes gets them, but that's a long way to drive for sometimes!
As far as you having too many fish, I wouldn't lose sleep over it. It's a lot, but I KNOW that some people on this forum push the envelope with their bio load all of the time. As long as you have lots of filtration, good water movement, and make sure you always do your water changes, you will probably be okay. There is a thread going in the reef tank forum where a guy has a 55 with 26 fish in it! P.S. I wouldn't recommend pushing it that far!!!!!!!!
Well, I think you'll be very happy with your new lights and the options it opens up for you. Good luck and happy shopping. If you want to give me your e-mail, I have a web site I would like to send you, if you don't mind. I'm not allowed to post it on this forum.