YSI 550A could take up to 10-15 minutes to stabilize before you can take a reading, The YSI optical O2 reades are ready almost immediately, but they cost more than the 550A.


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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).