I've tried this setting, which total costs $250
- Water cooler $100
- 12V 5A Electronic transformer $150
- Water pump (old one)
Test 1
10L water in air-conditioned environment (shown in the picture)
Success!

Temp drop from 24.6C to 21.5C
Test 2
24" tank with around 60L water
Fail! Temp remain the same even though it runs overnight
Conclusion
The result is unsatisfactory although I've used a very slow water flow

I think it would be useful for a very small tank only. I hope this information would be useful!