Missing Conch and rising nitrates

[aws2266]

I bought a conch a week ago, it buried itself within an hour of being released and I haven't seen it since. Algae hasn't been touched so I know it's not coming out at night. Now my nitrates are slowly rising. I went from 26ppm to 32ppm in a week. Concerned that I may have lost my conch. Am I overreacting or should I look for a dead conch? My nitrates and phosphates up to this point have been going down.

 

[juiceguy]

I have a couple of Conchs in my 290g with the same issue, I believe that by them burrowing in the sand, they are disturbing whatever denitrification the tank has established. My trates went from below 10 to 18 after the addition and have been hovering in that area. I usually can see the top of there shells where they are since they do not burrow that deep.