As luck would have it, I just recently hardscaped my 65 gal
. Tank with four left over junk rocks
I had stored. The big rock on the left weighs 40 lbs. The rock on the far right weighs 25 lbs. The hockey mask rock weighs 15 lbs and the remaining little rock weighs 10 lbs.
I bought the gravel at Lowe's for five bucks. The Holey Rock cost 20 cents a pound at my local rock yard. I believe it would stand up to most Oscars.