OLD PROBLEM

a few questions that I can think of
, what frequency are you doing water changes,
are you using carbon, and how often,
 I wonder if you are having ph swings?
your salintiy seems a bit low.
then there is the the nitrate,
how often do you feed? and what?

I do a 15 gallon water change once a month. I dont use carbon but I am going to as soon as I get my reactor. I have not noticed any ph swings in the last year. I know there is a little nitrate but that shouldnt be enough to kill the montis. I feed reef plus, zooplanckton, and dt's reef blend, for the corals. And I feed flake food and cube food everyday.

I would try carbon as soon as possible, that should remove any of the possible toxins, (don't add too fast though) I am a big fan of kalk, it has done really well for me over the last year, if I remember correctly it should also help with the nitrates.

it works best as a top off for evaporation, I am adding about gallon to two a day. although you must drip it in, you cannot add it all at once.

also except for one toadstool leather that I have kept, I did end up myself removing the leathers from my tank. I know that there are people that have kept both in their tanks, it was easier for me to remove them, ( I like the sps better myself)

I keep my salinity at 1.025 and have no problem with Montiporas. Your Alk is low too.

Correct me if I'm wrong, but isn't the salinity of the tropical ocean usually 35ppt, which is 1.0265 (specific gravity).  I know all the salt mixes tell us to have a lot lower salinity than that but it makes no sense.  If corals are taken from the ocean where the SG is 1.0265, then our tanks ought to be 1.0265 or very close to it.  You must have some tough acros to be thriving at 1.021.  An alk of 2.4 milliequivalents/liter (meq/l) is too low IMO.  My acros and montis do much better at 3.0 to 3.6 meq/l.  I try to keep my calcium at 425 ppm and my alk at 3.4 meq/l.  Add small doses of baking soda every day until your alk is higher.  Also, calibrate your refractometer with R.O. water to make sure it's giving you a true reading.  If you don't have a refractometer, check your hydrometer reading against someone with a good refractometer and then you'll know how to correct your measurement so you're getting a true reading.  Your lighting and water flow sound more than adequate and I agree toxins may be a problem.

Edited by faviasteve - January 06 2008 at 3:01pm

Here's the link.

I'm not trying to argue but this is where I got my info.  It's interesteing the "experts" can't even agree what 35ppt equals.

Quote from Randy Holmes-Farley, March 2007 Reefkeeping Magezine

http://reefkeeping.com/issues/2007-03/rhf/index.php

"For reference, natural ocean water has an average salinity of about 35 ppt, corresponding to a specific gravity of about 1.0264 and a conductivity of 53 mS/cm.  Salinity, however, does vary substantially from place to place.

As far as I know, little real evidence suggests that keeping a coral reef aquarium at anything other than natural salinity levels is preferable. It appears to be common practice to keep marine fish, and in many cases reef aquaria, at somewhat lower than natural salinity levels. This practice stems, at least in part, from the belief that fish are less stressed at reduced salinity. Substantial misunderstandings also arise among aquarists as to how specific gravity really relates to salinity, especially considering temperature effects.

The salinity on natural reefs has been discussed in previous articles. My recommendation is to maintain salinity at a natural level. If the organisms in the aquarium are from brackish environments with lower salinity, or from the Red Sea with higher salinity, selecting something other than 35 ppt may make good sense. Otherwise, I suggest targeting a salinity of 35 ppt (specific gravity = 1.0264; conductivity = 53 mS/cm).

Fortunately, coral reef aquaria seem rather forgiving with respect to salinity.  The range of salinities encountered in what most would proclaim as successful reef aquaria is actually quite large.  Don’t agonize over small deviations from natural seawater.  You will not notice any benefit changing from 36 or 34 ppt to 35 ppt (specific gravity = 1.0256 to 1.0271).  Many fine reef aquaria appear to run at salinity levels as low as 31 ppt (specific gravity = 1.023), but bear in mind that the values that aquarists report (as well as your own measurements) are fairly likely to be inaccurate, so pushing the low or high end of the range may not be prudent. 

Bear in mind that if aquarists target salinity values different than 35 ppt, the amounts of calcium, magnesium, alkalinity, etc., will all likely deviate from natural levels as well.  For example, making artificial seawater to a low salinity will normally result in low values for these parameters and may require adjustments."

Edited by faviasteve - January 06 2008 at 3:35pm

I don't know if I understand exactly why the relationship between PPT and SG varies with temperature, but I'll accept that it does.  35 ppt measures the amount of dissolved stuff in the saltwater and the SG of that saltwater shows the corresponding density increase (compared to pure water) because of that dissolved stuff.  When you look at simply, it seems the two should be exactly proportional, independant of the temperature.

Thanks for all the info guys.