In regards to your pm.
"RTN = ??? Tissue Necrosis.
Are you saying that GFO can cause the RTN?
Also, I HATE my Red Seas pH Test Kit. Everyone here says that pH test kits are the worst. Mine always reads the same thing. I was thinking of buying the instrument that tests for pH (not a refractometer) but I see that you have to keep them calibrated and the probes wet. I keep the fuge lights on from 2 pm to 7 am so I think my pH is relatively stable. Further, if it went up or down, I wouldn't know what to do to correct it back and I don't knwo where it's supposed to be.
Sooo, if I can't get a good reading and I don't know if the reading is in the desired range and I don't know what to do if it's outside that range, I figure with my 5-20% water changes every 3-5 days, I'm sticking my head in the sand and calling the pH good.
Any suggestions?"
RTN = Rapid tissue necrosis. Im not saying for sure i know GFO can or does cause RTN, ive just read many people believe that in there cases it has.
Ive never tried Red sea ph kits but yes most liquid color matching test kits are pretty hard to match colors, before i had a PH monitor i always used API PH liquid test. Only takes 5 drops to 5 mil. of tank water and I didnt think the color chart was to hard to get a general idea if it was too high or low.
Yes PH monitors do need calibrated every few months 3-6 and they do need to be kept wet, but thats easy with a probe holder in your sump, and you get a constant reading of what ur PH is at.
Yes Having a refugium on a reverse lighting from main tank can help from major ph shifts over night. But i still think its a good idea to regularly test your ph if you dont have a monitor.
Ph is generaly acceptable at 7.8-8.5, but even better to be held consistantly at the 8-8.3 range.
So many things can come in to play on how to correct high and low PH levels, the relationship between Calcium/ alk/ mag/ph is one of the most confusing parts of reef keeping IMO.
Here are a few reef chemistry articles.
The "How To" Guide to Reef Aquarium Chemistry for Beginners, Part 3: pH
http://reefkeeping.com/issues/2007-05/rhf/index.php
Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.htm
High pH: Causes and Cures
http://reefkeeping.com/issues/2005-03/rhf/index.htm
A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH
http://reefkeeping.com/issues/2006-06/rhf/index.php
Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm