I am impressed by the direction this thread has taken. Several years ago it would have been much different. There would have been all kinds of theories proposed. Not enough sand bed infauna, sand not deep enough, not enough clean up crew, lack of biodiversity, lack of nutrients, fuge not big enough........ It's good to see that we're getting away from this type of thinking.
I like the "LARS" thing, but don't think that's the case with every old tank problem. I make a living, at least in part, by helping people through tank problems. What I often find is that the problem isn't laziness. Usually, when it is laziness, the reefer already knows what the problem is. The problem is often a product of misinformation, or a lack of understanding. Many hobbyists that I talk to are afraid of water changes, or doing much of anything to their systems. They fear that they will remove to many "good" bacteria, or to much of the needed nutrients in the system, or that a large water change may shock and kill everything in the tank. All of which is simply absurd.
The reality is that we shouldn't call this OTS (old tank syndrome) It should be called DTS (dirty tank syndrome). Tanks don't suffer because they get old. They suffer because they get dirty. Just as with any other animal we keep in a small enclosure, if we force them to live in their own filth, they are highly likely to become ill and die. If we keep that enclosure clean, the animal is much more likely to live a long healthy life. In this regard, coral and fish are no different that hamsters and birds, or virtually any other animal we keep in small enclosures.
The reason that many tanks run into problems after they have aged a bit, is that the maintenance and filtration simply isn't quite keeping up. (NOTHING IS PERFECT) Lets say the maintenance and filtration is handling 99% of the organic / nutrient / waste build up over a weeks time. That means that 1% of the food we add in that week remains within the system. Now 1% isn't enough to do much of anything, so while the tank is young, everything seems great. It isn't until that 1% is added to the 1% from the week before, and to the week before that, and ................. Over time, this can build to problem causing levels. Often the hobbyist is confused. They've been doing their weekly 10% water change, ritualistically, just like the book told them to. They're doing everything "right", and don't understand why their tank is going down hill. We need to start looking at the home we provide to our coral and fish more like our own homes. We all have routine maintenance we perform in our homes. We sweep, mop, dust, do the dishes, and take out the garbage. Rarely is this sufficient to keep up. Over time filth just manages to build up. This is when we do our "spring cleaning". We wash down door jams, take the curtains down and wash them, move the furniture and clean under it....... We should be doing the same thing to our systems. Periodically do a LARGE water change, clean the crud out of the bottom of those overflow boxes, clean the sump, skimmer body, and all those other devices, get behind the rocks and remove the crud that's there. If everyone could start doing this, OTS would become a thing of the past.
Peace:wavehand:
EC