Putty/Concrete super weak?! Is glue better?

[onlytoby]

Just a quick question about the rock putty and concretes, I bought both however both seem to be quite fragile.
The concrete crumbled when I tried to put the rocks in the tank originally after a few days of setting and I was just doing a water change and slightly touched the now puttied rock and they came apart.

The rocks aren't really supporting any weight at all, it's just two pieces leaning on each other to form an archway but I'm just concerned a fish might get injured!

Would glue be a better alternative?

 

[CoastieFlo]

I ran into this problem before, put some super glue between the putty. So putty on each piece of connecting rock with super glue between like a sandwhich... it helped it set for me, also it will cure in the water.

 

[davidcalgary29]

I ran into this problem before, put some super glue between the putty. So putty on each piece of connecting rock with super glue between like a sandwhich... it helped it set for me, also it will cure in the water.

+1, and make it a gel superglue. The regular stuff just floats off whenever I try to use it in my tanks.