Join Date: Jul 2014
Location: Swamps of Texas
The wood will basically be water weight after being soaked, so it weighs about the same as the water it displaces.
1.5 foot cube will hold 210 pounds of water (25 gallons.) 35 pounds of rock should not be a problem. Same deal as the wood, it will displace some water. Net difference is a little bit. Not enough to matter as long as the tank is in good condition.
I'd say everyone else does it, so it's fine.
Magical moments can be fun. Those others, not so much. LOL!