Also, if you have a lot of Malaysian trumpet snails in your tanks, O+ might not be ideal, because they will disturb the gravel/substrate and move the pellets up exposed... I learned the hard way when my mts disturbed my amazonia aquasoil sub with O+ tabs like crazy and a lot of the pellets moved up to the surface.. My bad experience, but luckily nothing too bad came with it; however I had a lot of pellets on the surface.. didn't look so appealing. So yeah, like devilduck said, you have to becareful with it and make sure you don't have a lot of mts population in your tank. I still have a lot of it in jugs..
55 gallon Rainbowfish species/Harlequin rasboras community Dutch scape low-tech planted tank
60 gallon Bala shark low-tech planted tank
250 gallon Community Tiger Oscar/Red hook silver dollar/Silver dollars/BR Parrots/ PB Jack Dempsey/Clown loaches/Tinfoil barb/Roseline sharks/Barbs Monster fish tank