Advise on 4" blocks

[Ronfire]

Looking for advise on 16x8x4 blocks. I have a line on some of these blocks for a good price but unsure if it will work for me. I am planning on building an approximate 10'x12' pond 4' to 6' deep. The catch is that it will be on a slope and will have a 6' high section with little back fill except rocks to make it match the yard retaining walls. The blocks are notched so I can place horizontal reinforcing rods every layer. I also plan to use a liner inside the blocks so cracks do not become an issue.
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Here is a photo of the area I am looking to build. The far end would be slightly above grade .

 

[addy1]

Just read this. Sorry your post was missed. I have not used bricks or blocks in any of my builds. But @RobAmy
is a great stone Mason. Maybe he can help you.

I would think using the blocks with reinforcing rods would work.

 

[RobAmy]

The blocks you show are not very good for what you are describing, even with reinforcement. I would go with a minimum for 12" in depth, the block you have are only 4" depth. I would use rebar vertically into footings. Block wire is a good idea too for a 6ft high retaining wall.