Anything under 33 gallons (im canadian and cant convert to litres well yet, sorry) is considered a nano reef aquarium, and recommended for experts only. But, if you were to get some advice from the experts on this site, Im sure you could set one up. How much expirience do you have with freshwater and/or fish only saltwater? Although freshwater is a world away from saltwater, it can still help to get some expirience with freshwater first.
And a protein skimmer? if you understand the concept of a skimmer, it is actually very simple to construct your own custom model(oh sorry, you already have!). For light? all you need to do is run down to the store and pickup a few bulb compact flourescents, and mount them on to some sockets in the hood. Animals? well, if clownfish are your fancy, you could have a pair of small
amphiprion species, with a few pounds of live rock and sand, with some crabs, maybe a small shrimp, some tough snails, and a nice big anemone right in the middle. I have a ten gallon that I might turn into a nano, and ive calculated the price of the hardware, including a filter and a heater, plus the LR and LS, to be under $300, and even with the animals, being way less than $500 total.
Nanos can look absolutely beautiful when maintained, but i personally prefer bigger tanks, because they often look just as or more beautiful and you have more room for animals. also, i have been told(and now believe) that the protein skimmer takes care of most things that a water change would remove, and I only do water changes, on all of my tanks, every few months. But you might not want to listen to me
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Good luck on the tank
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