The clouds are beginning to part, but it's still a little foggy. First, a "reputable" LFS
is a myth just like the loch ness monster.
Just kidding I am sure there are a few. Your store was correct for the most part on the "berlin" method of filtration. However a lot of factors come into play with that. The most important being your LR
. I can tell you now, that you simply don't have enough to provide adequate biological filtration for your current fish load. You more than likey need twice as much, which would then make your tank nearly too small for a tang. I am unfamiliar with a "diamond" shaped tank off the top of my head, but it may be "do-able" for a tang. *shrugs* You say you started up with the "best" live sand. If it came in sealed bags off the shelf, it was not only NOT live, but NOT the best either. But again it will do if you have enough of it. How much did you start with? Another thing that is eating at me, is that you say you use Instant Ocean when needed. What do you mean by "needed"? You don't add it directly to the tank do you?
Ok a breif description of a water change: With good water a salt mix is added in a bucket or a tub and pixed with a small pump until SG
, temp, and pH match your existing tank water. Then old water is removed from the tank and replaced with the new water. This should be done at least bi-monthly or as needed. You probably need a 20% water change daily until your nitrates are under control.
Keep us posted. Good luck and use us as much as you need. That's what we are here for!!