Here are some thoughts about some of the issues I just read about when catching up on this thread:
Custom plumbing?
In case you plan to spend a lot of money having someone build you something custom, remember that 1" heavy duty (schedule 80) bulkheads will fit nicely into 2" holes like you have, and are available on the internet. The DIY (Do-It-Yourself) forums (like on nano-reef.com) are filled with examples of 1" overflows that you can put together very cheaply. For example, look at the diagram in
THIS THREAD. In addition to a bulkhead, it uses a PVC T fitting, an end cap, and a couple 5 cm (or so) lengths of PVC pipe. You would only need to run PVC pipe down into your filter sock, or attach a PVC to hose-bar adapter fitting (also available on the internet) and run flexible vinyl tubing down to your filter sock.
Broken thermometer:
Those aren't mercury beads in the thermometer, they are steel, and are only in there for weight (mercury, although metal, is a liquid (like the bad terminator inTerminator II)). You broke an alcohol thermometer, and unless you broke the tall thin part on the inside that holds (held?) the red liquid, you only broke the housing. The little steel balls will rust in salt water, but it sounds like you got them all out. If not, a tiny bit of rust isn't a problem (is it?)
Refugium:
The bacteria on your live rock convert ammonia (animal waste) to nitrite and then to nitrate. Some of the nitrate will be converted to nitrogen gas by your live rock, but most of it will just build up in your water until you remove it. You can remove it by doing water changes (which you should do anyway), and by a few other means. The primary purpose of a refugium is to move the nitrate that builds up in your water into the tissue of live plants. You then trim, and discard, which finally removes the nitrate from your system. Nitrogen (nitrate) is a fertilizer, which "macro algae" (plants) will take from the water and use to grow. You need to read all about refugiums to get the big picture, but the short version is that you provide light, a slow flow of water, and few starter plants, and as they grow, they will remove nitrate from your water. Then you trim them as needed. A refugium is a good idea, but it's mostly just a way to avoid more frequent water changes, so you can post pone setting up the refugium if you're willing to do the extra water changes.
Size for clown fish tank:
My father in law keeps a maroon clown in a 3 gallon nano tank, so anything larger than 11 liters should be fine. However, as you are learning with your buckets, there are special challenges involved with keeping a nano tank (which is any tank less than about 115 liters). Have you considered just running a little tank (say 20 liters) in series with your large tank? Why set up a totally separate tank when you could simply pump water from your sump up into a small tank, and let it overflow out of the small tank back into the sump (or into your main display tank)? That way, the water quality for your clown fish will be as stable as in your large tank. Small self-contained systems (nano tanks) are much more vulnerable to small changes (a single over feeding, or a single undetected dead animal) than a system with a large water volume. For the ultimate in simplicity, you could just keep your clown fish in a little tank that is submerged 90% submerged in your main tank. You could branch 5% of the flow from your return pump into the clown tank, and let it overflow into the main tank. As long as the octopus can't reach into the clown tank, it should all work. Just a thought.
Fan:
When water evaporates it removes a significant amount of heat (which is why sweating cools you off) so the point of a fan is to cause as much evaporation as possible. So mount it so that it is blowing directly on the surface of the water in your main display tank (or in your buckets. The down side is that all the water that evaporates will leave its salt behind, so the salinity of the water that is left will increase as evaporation increases. You must add RO/DI water (without any salt in it!) to the tank to replace what evaporates, so ideally mark the water level, and just refill up to that mark with fresh RO/DI water every day.
Buying the anemone:
It may not have been a rookie move, it may have been a calculated risk. You have very limited access to fish stores in Oslo, and you seized the opportunity when you had it, knowing that you were taking a chance. But failing to act when a rare opportunity is presented, is also taking a chance. Maybe the rules are different when you live on the edge of the world.
I hope some of that helps.
I'm relieved! I did read up on that particular anemone and its requirements before purchase so it wasn't entirely impulse; the issue was I was in Oslo where I don't get to go often, and it's really the only place to buy saltwater stuff and bring it home that's within any kind of driving range - my ability to get there depends entirely on Thomas's busy schedule. Anyway, I didn't know whether the colours on the underside were a sign of injury or something, so it's good that it looks ok to you.
). I have one tank with only 1 drain and a 90 degree elbow, air gets trapped when the pump cuts off and has causes some minor issues (that could be major if the thing did not clear and no one was home). I hate plumbing as well 
