No. Doesn't look like parasites. You don't need the stressZyme either - I've never used it. If it's one of those "bacteria in a bottle" things, then opinion's divided about whether they do any good whatsoever.
[Edit - just checked, yes it is 'bacteria in a bottle'...]
I think your tank will be healthier by you saving yourself work cleaning the sponges and money by leaving out the stressZyme
The best work you can put into maintaining your aquarium is regular water changes.
[Edit - just checked, yes it is 'bacteria in a bottle'...]
I think your tank will be healthier by you saving yourself work cleaning the sponges and money by leaving out the stressZyme