laga77
New member
I was a foreman in all forms of concrete construction for over thirty years. A 300 gallon tank is going to weigh around 2600-2800 pounds. A 8x4 pad is 32 sq. ft. That is less than 100 pounds per sq. ft. Go into the basement and stand with your feet together and you are applying more pressure than that. A tank of water is dead weight. It is not a piece of machinery that is going to vibrate and move and create lateral movement. Your floor is 120 years old. If you dig it up you will only loosen what has settled. A 4 inch pad on top of the floor with 1/2 inch bar @ 12 inch center would be overkill, especially with a wooden stand.