i appreciate everyones response, perhaps this may help:
from a previous thread, some of you may know i decided to rebuild my sump which fell apart shortly after starting up. this tank had previously been run without a sump, with no end to problems...(the reasons why we took that approach are a long post in and of itself, and too much of a tangent for here)
so sometime last week i drain the sump, putting the cheato and live rock from the fuge into a separate holding tank, filled with water from the sump. this tank was not heated. a bag of chemipure and one of phosguard was put into another tank and allowed to dry (no particular reason for that, i couldve just as easily thrown it in with the live rock&cheato)
after drying out the 55 gal tank, i siliconed my 1/4" baffles into the tank and let everything cure for 48 hours.
following that, i had added 30 gallons of RO water + salt and a small recirculating pump. i allowed 24-36 hours of time for the salt to dissolve and the water to heat up
the tanks salt level was high- approaching 1.03 and the sump was about 1.023. i included some fresh RO water to help even out the salinity somewhere in the middle
shortly after my sump "went live" i placed the live rock into the sump as well as 20 ml of marin fauna ultra algaex . this is the dosage for 100 gallons (approx the amount in the tank and sump). ive posted pics of the level of algae im plagued with elsewhere. i also added the chemipure (which probably promptly removed the ultra algaex)and phosguard.
the previous day i had done a water change somewhere between 30-40% (i cant remember which) and up until this point(trying to remove phosphates), all fish were acting normally
several hours after i started up the sump, my room mate went down to get something from the basement, and came up to let me know there was something wrong with the tank
i went down to find virtually all fish in obvious distress, some panting very rapidly
the first casualty was my flame angel- it was laying on its side, breathing shallowly. i bagged it up and tried acclimating it to known good water in another tank. it didnt make it
shortly after, my coral beauty had gone from frantically swimming to being too weak to swim away from a tunze powerhead (the smallest of the turbelles). i tried taking that one upstairs and trying to acclimate it to the coral tank, but again, it was too late
what may be the next death (its still hanging in there, but still panting and its breathing is very labored) is my lavender tang, who was sitting with its belly on the bottom of the tank, still upright but unable to swim
other fish were discolored when visible (such as a starry blenny which turned yellow)
at this point i cut off the sump, and tested the water..nitrates 0, ph 8.2 but phosphates were showing 2 on the api test (IIRC) and ammonia was .5 ppm (the silicone mentioned releasing ammonia and methane during the curing process, but i didnt even put water in the sump till it had 2 days curing time and and additional day or day and a half of having water recirculating thru it, so it had 3-3.5 days to off-gas that ammonia)
i did an emergency water change, i had 30 gallons of RO water, but it was sitting at 58 degrees, so i put every water heater i own into a 5 gal bucket and 1kw of heating power (8.3 amps according to every electricians friend, georg ohm) would bring 5 gallons of cold water up to 75-80 deg. within 10 minutes or so. theoretically, this should reduce the concentration of whatever the root cause is by the percentage of water changed, and when i went to bed, everyone seemed to be doing better
as of 5 this morning, everyone looked dead, and like i mentioned, im no stranger to what early morning tanks look like but within the context of the previous nights issues and the fact i was running late to work and couldnt investigate the problem as much as i wouldve liked to, i could only conclude i woke up to a dead aquarium. the only one showing any signs of life were the two clowns (acting normal) and lavender tang (acting much worse..breathing much more labored and color now gone)
later my room mate confirmed everyone survived the night, so i came home and did another ammonia test and 30 gallon water change. surprisingly, my ammonia test *still* showed .5 ppm (either theres an issue with the test, or something in the tank is generating far more ammonia than ever before. my live rock is a mix of cured LR and dead rock, but these issues came on over a period of just a few hours) . my ro water showed 0 ppm, and oddly enough, freshly mixed saltwater showed races, perhaps .25 ppm or more. i struggled through chemistry class so my understanding is better than "the tests are black magic" but not a whole lot better than that. still it doesnt seem like the reagents should be different between freshwater ammonia tests and saltwater ones. nh3/nh4 is nh3/nh4. still, i could be wrong about that)
so, yea, i changed out 30 gallons this evening. my fish arent out of the woods yet, but most look like theyll make it. both tangs are taking this particularly hard though.
hoping to see better days and everyone still alive tomorrow. hope i didnt forget any details