1. Living Waters: Black Tiger Prawns live in relatively deeper and higher quality waters, while the Keelboat Prawns are mostly found in shallow or freshwater areas, which may result in less contamination of the Black Tiger Prawns.
2. Shrimp line: The shrimp line of black tiger shrimp is almost invisible, while the shrimp line of the basiji shrimp is more obvious, which also indicates that the black tiger shrimp is cleaner.
3. Growing environment: Keelboat shrimp are freshwater bred and raised in seawater, while black tiger shrimp are grown entirely in seawater, which also indicates that black tiger shrimp may live in a cleaner environment.
Combining the above comparisons, the black tiger prawn is significantly cleaner than the Keelboat. However, it's worth noting that either type of shrimp should be avoided if they are found to have a noticeable contamination or odor on their surface.