I had a Six Line Wrasse in my 29 gallon aquarium with a Coral Beauty and had no issue. If I were you I would get one! They are very neat looking fish and very active between the rocks. Mine Jumped out and died unfortunately. :-( I replaced him with a Lyretail Wrasse in my bigger tank. I was upset, but I love my wrasse now!
A six line Wrasse is good for eating bristleworms and keeping them in check.
Stay away from the mandarin for now! They require a established tank with a large colony of pods
. They will even go though the established pods
really fast in an established tank, that's why you would need a place for the pods
to grow and live without being eaten so they can be continually fed into the main tank for the mandarin. A big headache, but worth it! If you want to set all that up and wait for a year or two before you get one.
As far as everything. I would get rid of all the water for sure! Stir up your sand really good and suck out all of the cloudy water that it produces. This will loosen up the sand and get all the gas bubbles out and anything really dirty out of the sand before you put new water back in.
I would recommend a full cycle, just to be safe. It won't take too long if the tank is housing good bacteria already. Get yourself a good test kit and go from there. Before you put any fish in, your ammonia should be at 0. You need an ammonia source, so my suggestion would be to go to the store and buy yourself a few large uncooked shrimp. Get some clean stockings and throw the shrimp in the stockings and hang them in your tank. Once the tank starts to read a ammonia spike, you are cycling! Once the ammonia reaches 0 after the spike you are done! Do a massive water change (I did 80%), and fill it back up and go to the fishy store! Took me three weeks because of all the live rock and sand I bought!
Add fish slowly after! One or two at a time, and give it a week or two in between adding. Once you put your fish in, keep testing so you know if your tank is ready for more. Your ammonia should always be 0 even after you put fish in. If it goes up at anytime, I would do a 50% water change and keep testing each day until it reads 0 every day! This is only for the first few months of your tank, I cut back on testing to twice a week once I was established and had everything running smoothly.
Here is my advice for your live stock. Go here:
Saltwater Fish: Marine Aquarium Fish for Saltwater Aquariums
Look up all the fish you would want that could fit in your tank, than check computability. The reason I say this and not tell you what to get is because my list changed 100 times before I was finished adding fish to my tank. As long as a fish is compatible with any of the fish you currently have, your tank is not overstocked already, and it can live in your size tank, go for it! Just remember, a understocked tank is a better tank! Especially if you are moving again within a year! Because the less you have, the less of a headache you will have moving your tank and breaking it down for travel. It also makes keeping it clean easier!