Tank is running a huge external filter, does 100 litres an hour
@Morri - I believe he's using a canister filter. He also said he will be putting live rock in there next weekend.
@Pearsondesign - Welcome back to the salty world of fish keeping! Your old 7 footer sounds like a wicked tank lol.
I'd advise you to add the live rock whenever you can because the cycle won't truly start until the LR is added. Some of the beneficial bacteria in the new live rock will die off and you will have spikes in ammonia and nitrites so you will have to wait for the complete cycle anyway.
Sand is there to help with filtration so you might want to reconsider. Not having sand wouldn't necessarily eliminate bad algae problems but it would reduce the chances of food and fish poo getting buried in the sand. Normally adding a sand sifting goby would help with sand turnover so that food won't get sandwiched by the sand but some gobies don't do well in aquariums as they can be hard to feed sometimes.
Coralline algae will eventually grow everywhere and it isn't really essential for it to grow on the bottom surface of the tank, unless that is the look you are going for. Sand, as a substrate, is useful in many ways, but it also serves as a cushion for any rocks that may fall or tip over. Without sand, rocks could shift, scratch or dent the tank, or fall on the bottom and crack the tank. I think you know where I'm going with this lol. I'd say get some sand, even if it only fills up half an inch. The benefits outweigh any negatives of having sand substrate.
With protein skimmers, it really is a matter of opinion. Some people have done fine without any skimmers while some have had extreme crashes in their tanks without one. A factor in your consideration of purchasing a protein skimmer would be whether or not you plan on keeping corals. Most corals need pristine water conditions and a skimmer helps you with maintaining good water quality. Another factor would be the amount of fish you plan on having in your aquarium. Obviously, with more fish , the bigger the bio load, which means you need more equipment to help you keep the water quality as good as possible. I see that you have added some marine plants, which also help in the filtration process (unless they are fake, I can't really tell from the picture
). That being said, water changes are essential in keeping the "bad chemicals" down and regardless of having a protein skimmer or not, they should be done on a regular basis, usually weekly or bi-weekly. If you don't have a skimmer, you might have to do more frequent water changes.
As for the aiptasia I would recommend you to remove it ASAP as they will spread like crazy. Some common methods are to burn the heck out of it with a torch, pour hot water on it (although this is not always effective), or buying chemicals to remove it, such as JoesJuice. Some people have said that squirting lemon juice directly into it's mouth will kill it but I have yet to have tried this method or see it in action.
I'm guessing you have a 4' tank? Maybe 90 gallons? That's a pretty good size tank as you'll be able to house a few things. In my opinion 2 percs would be fine in the 90 gal tank but some might disagree. Firefish gobies are nice looking fish, and they do especially well in groups, as they live in groups in the wild. Blennies are one of my favourite fish, especially the bi-colour blenny. They have really neat personalities and are quite comical to watch sometimes. Flame angels are pretty looking fish but if you plan on keeping corals, you should take caution, as some nip at corals while some don't, it's really a hit or miss with any kind of angel fish. Even though you said you probably won't get damsels, I would advise against them anyway. Since you are getting percs (they are related to damsels), they will probably fight to the death. Suffice it to say that clownfish should never be added with damsels, less you want dead fish. You might be able to sneak a yellow tang or scopas tang into your tank if you really want to. Hawkfish are also really neat fish that I've always wanted but they will have a go at inverts (snails, shrimp, hermit crabs, etc.). Other than that, it would really depend on if you wanted to keep corals or not. If there are any fish that really stand out for you feel free to ask if they would be ok for your tank, as there are too many to think of off the top of my head.
WOW I typed a lot
. Anyway looking forward to seeing your tank progress. Don't forget to keep us updated! Good luck, and don't forget the most important part; have fun!