Ok lets just speculate here and accept the tanks are failing because of some "Three year old Syndrome". What is causing the failure? Rocks getting too full detritus? Sandbed is breeding some micro nasty? The corals themselves reach a point in growth that they somehow cause a tank to fail?
If it was a sandbed issue then tanks without sand would not be effected. If "Three year old Syndrome" were real then some comparison might reveal a common denominator in the failed tanks. Perhaps someone with time and skill could troll the boards looking at failed tanks and do some comparison analysis.
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