You don't need to buy shock; the reason is you already are!

All normal 'shocks' are primarily based on one of 5 chlorine compounds, listed in order of frequency:
1. dichlor, also sold under 100's of names
2. calcium hypochlorite, sold under 100's of different names.
3. sodium hypochlorite or bleach, sometimes sold as "Liquid Shock"
4. trichlor, sold as an anti-algae powder for concrete pools, but rarely blended with dichlor as a shock
5. lithium hypochlorite, sold as quick dissolving non-stabilized shock.

Only #1 and #2 are really common. But they are often diluted with other materials, including borax, magnesium sulfate, aluminum sulfate, copper sulfate, potassium monopersulfate, and so on. You are better off with the PLAIN dichlor or bleach.

Oh yeah. Be sure to check the % of the Aldi bleach. Most standard bleach is now 8.25%