I could carefully visually inspect the clam.
Pyramid snail eggs and flatworm eggs are not affected by most dips, you need to manually remove the eggs. With clams a good physical inspection is important, does the clam have ruffled edges to the mantle, are there snails found at the base or chutes, are there boring worms on the shell, does the clam react quickly and appropriately to shadow and movement, is the color good, is the mantle fully extended, is the clam gaping?
Long story short I sometimes used to scrub the shell in a FW dip with a soft tooth brush, then burp the clam before putting it in the display, but the initial inspection was the most important.