The photo is of our two German Shepherd puppies, Maya left and Oso right, at about seven weeks. They were “helping” me move the concrete blocks into the greenhouses.
Since we went to floor gutters with walkways in our greenhouses starting in 2002, we’ve used walkways constructed of wooden 2X4s and 1X4s. From the beginning we had problems with the boards breaking, usually when carrying bucket full of fish or worse a “slop” bucket full of “gunk.” We tried reinforcing the walkways with additional 2X4s. We used marine paint to prevent rot. Nothing worked and we couldn’t use treated wood, which is rot resistant, because treated wood contains arsenic, which is too toxic to the fish.
Then, it occurred to me that concrete blocks would be perfect. They are rot proof and almost indestructible. They, in keeping with my philosophy of using fungible and reusable materials, can be used for other purposes if replaced later. They aren’t expensive. So, we’ve started replacing wooden walkways with concrete blocks. Since our water is already rock-hard and our pH between 8 and 8.5, there is really no liability to the use of the blocks. The only drawback is the labor of carrying the blocks and putting them in place.