Yes the one that last 9 days was with fine sand the previous one was coarse sand/ gravel. Sand does not get in the filter, it's nowhere near the bottom and I use a pre filterSo I remembered another thread and yup I found it. Are these both from the tank you added sand to about 6 weeks ago? Not saying it's the sand, but if it's the same tank, I thought that sand was super fine or something.
I would suspect a fliter with or without sand would last 2 weeks. I saw very little sand in the housing the intake tube filter keeps most of it outSand does do a number on the HOB'S but the older AQ 500's are quality especially if you can find NOS.
Could be bad luck, I bought both of them from the same PetSmart since they are 80 in-store price.I get it. I was just brainstorming.
No clue on why you'd have problems with 2 other than bad luck. Obviously if they were losing them that fast, it would be well known, but it's always possible that one particular plant had a problem and you may have gotten 2 from the same plant.
At one of the plants I worked at, we had a sensor go out inside one of the extruders, and we didn't know the temperature in one area inside it was about 100 F lower than it was supposed to be. For several weeks, everything that came out looked good, but the defects began becoming obvious a few weeks later.
Mechanical things like this might take months to show up.