Those blocks are made of calcium sulfate ("plaster-of-Paris") with some cornstarch to speed the dissolving. Unfortunately, you can't simply "frontload" the fish by overfeeding them just before you go.
The CaSO4 doesn't affect the alkalinity ("KH")-- no carbonates-- but it does add to the general hardness or total dissolved solids.
If you leave them hungry instead for ten days, they'll just settle into a quieter mode and pick at the plantings. In nature many species go for many weeks during the dry season with little to eat. You might turn the heat down a notch (within their comfort zone of course) to help them slow their metabolism.
When you see how clear the water is when you come back, you may even rethink your feeding schedule. Giving the fish a "starve day" every week is hard to do, but very responsible....
The CaSO4 doesn't affect the alkalinity ("KH")-- no carbonates-- but it does add to the general hardness or total dissolved solids.
If you leave them hungry instead for ten days, they'll just settle into a quieter mode and pick at the plantings. In nature many species go for many weeks during the dry season with little to eat. You might turn the heat down a notch (within their comfort zone of course) to help them slow their metabolism.
When you see how clear the water is when you come back, you may even rethink your feeding schedule. Giving the fish a "starve day" every week is hard to do, but very responsible....