"Water changes and carbon. You have to keep that nitrate way down. When you say you lost a 8" gigas. Did he die in the tank and release from the shell?"
I consistently run carbon and change it out every 4-5 days. I took the clam out before he completely deteriorated and finished detaching from his shell.
"Sounds like mentioned, your not keeping up enough with water changes, do some frequent & large volume changes until things get better, this will always help when you can't explain problems, can't hurt either If your making water up properly."
In the past month I have probably changed 75-100% of the water in the system trying to bring the nitrate down. Unsuccessfully. All water made is with RO/DI.
"What are the dimensions of the tank ?"
60" x 18 x 20h
"Where are they placed and how far from the lights ?
The Gigas was placed on the sand bed approximately 22" from lighting.
The other two clams were placed higher up on the rockwork roughly 15" from MH's.
"What type of lighting are you using and how many watts?"
I am using two 250w MHs (pfo ballast) 14k bulbs. Supplemented with two 96watt pc's.
"What is your current fish list ?"
3 Tangs, 2 Percula, and 1 yellow tail damsel.
"Have you examined the clams carefully for any pyramid snails?"
I am familiar with pyramid snails and have found no evidence of any on any of the clams within my tank.
"What are you using to maintain your cal/alk levels and how often are you testing?"
I am using Seachem's Reef advantage calcium and Reef Pure marine KH buffer. Since I have been having trouble maintaining my calcium levels over the past 6-7 months I usually test every 4 days.
"nitrates at a level of 50ppm is high and may be detrimental to the over all health of the tank but wont have a deadly effect on clams. on the other hand having even a detectable amount of nitrites leads me to believe you have something else going on."
It was my understanding that over time nitrate within the water column will eventually break down into ammonium. My ammonium levels have alway been undetectable and my nitrite levels are also undetectable using Salifert test kits. The Salifert test kit allows for more sensitive testing depending upon how you take the reading, which inturn translated into .o1ppm which is actually considered undetectable by Saliferts method for nitite testing.
What makes little sense is the fact that ammonium is oxidized into nitite which is then further oxidized into nitrate, but both my ammonium and nitite levels have always been undetectable.
Also I would love to have a refugium which could contain chaeto, but unfortunately I do not have the room for this.