[abcha0s]

Only a qualified structural engineer can answer your question. They would need come come to your house and do a survey. Otherwise, the best that you can hope for is an opinion.

Your tank will carry a weight of nearly 4000 pounds. I can tell you that the floor was not designed for this weight. That does not mean that it wont support it just fine, only that the building codes never considered 300 gallon aquariums.

I think the risk is the floor settling and the tank going out of level.

I tried to convience my wife to put my 300g on the main floor. In the end, she convienced me to put it in the basement. Neither of us really knew if there would be problems with having it upstairs, but that's exactly the point. Neither of us really knew.

I think it's a question of how comfortable you are with risk. You will probably be fine, but what exactly does probably mean?

There are some good articles on the web that explain exactly this question. However, they say basically the same thing but with a much better explination of what's going on in your floor. It's interesting though. My wife and I both found the same article and both presented it as the basis of our position. The author can't really say whether it will be safe or not, so the article is subject to interpretation of opinion.

My guess is that if you asked everyone on Canreef, you'd end up with a 50/50 split opinion.