How much is to much

I actually have one with calarpa (sp) I don't have bio balls but do have about 30 lbs of live rock there.

 

Thanks for bearing with me. I am a stickler for detail and complete information. The reason I was asking was because your post, while secondarily was about water changes, I thought it was primarily about Nitrate controll, hence the reason for more info. In this hobby, all too many times, one problem may be a result of a combination of events or other factors. Example; lights losing their spectrum + neglected canister filter + a little over feeding and BAM algae out break! Now, this doesn't apply to you but I think you see my point. Now, looking at your info I really don't see anything that jumps out at me and as I said earlier, you really do not have "high" Nitrates. Have you posted a pic somewhere already? If not post one here or PM me, I love seeing what others are doing.

 

No, Thanks for helping.. The only thing I can think is that my tank is pretty stocked for how new it is. I know I broke the rule. I agree that they are not real high, it's just that my levels are normally 0 so I'm feeling a little paniced that they are off of that number.

Here is a link to my tank thread--- and K+ for looking beyond the question and trying to get to route cause..

http://www.3reef.com/forums/show-off-your-fish-tanks/remickjs-120-gallon-reef-thread-55016.html

 

Since you have a 120G tank, doing a 15G WC comes out to about 12% of the water volume. For ease of mathematics, let's say it's 10%. Since you have 20ppm NO3, you are also removing 10% of said NO3 with the 10% WC. That means you are dropping your NO3 down to 18ppm. To get your NO3 under control, you have to find the source of your NO3. Doing a WC will only slow down the buildup of toxins, not remove them. Your system is constantly producing NH3, NO2 and NO3. Even doing a 50% WC will drop it to 10ppm, and that is assuming your tank isn't producing in the mean time.
The source can be as simple as feeding a little too much, a dirty filter floss that needs to be cleaned, a dead snail under a rock, etc. Finding the cause is much more important than trying to make a quick fix. I've been there, done that in the past, and doing the quick fix (i.e. >50% WC) usually throws off all of the water chemistry levels and leads to an UGLY system crash. Just take it slow and easy and look for obvious causes and go from there. Good luck with it, just take peace in knowing 20ppm isn't as critical as 200ppm.