I know this thread is a few weeks old - but I thought I'd just add a bit to it.
I bought a new bottle of Interpet Anti Whitespot a couple of months ago when some new fish came out in spots. I didn't look at the ingredients, I just used it and it worked fine.
In the last couple of weeks, though, I've had a more serious outbreak of whitespot, following a problem with aeration in the tank. One of the fish also had what could have been a fungal growth on his eye - so I used Waterlife's Protozin which says it's also anti-fungal. Once again I didn't look at the ingredients (terrible admission for an ex-biochemist) I just used it.
Not so successful this time! Fish with the eye problem died (I had transferred him to a hospital tank by then) and white spot was getting worse. Had run out of Protozin, mid-course, so got a new bottle and this time read the directions on both bottles. I think all fish medications are now getting more ingredients listed on them.
Interpet Anti Whitespot has Formaldehyde (approx. 4.5% w/v - which seems very high) and Malachite Green (approx. 0.05% w/v) as active ingredients - in spite of being blue, not green. It will be the formaldehyde that is carcinogenic - malachite green is just toxic!. If you get a mouthful - spit it out and rinse your mouth with water - don't swallow it!!
The Protozin, on the other hand, contains a slightly higher level of Malachite Green (0.085% w/w), a
very much lower level of formaldehyde (0.07% w/w - hence their label only says irritant - not potential carcinogen) and also contains Copper Sulphate (0.015% w/w). The new bottle also had a warning against using it in tanks with shrimps in.
I was a bit alarmed by this news, since I have Amano shrimp in my tank and had already given them a couple of full doses - so I halved the dose (as recommended for sensitive species) and e-mailed Waterlife (who are brilliant at getting back to you in answer to queries - I've tried them before). I suspected they must have changed the formula.
Turns out they haven't changed the formula at all - they've just had some complaints about shrimps dying. They've tested Protozin in their laboratories and not found any ill effects on shrimp - but have put the warning on the bottle, just to be on the safe side.
I then had to decide which treatment to use next - another dose of Protozin or try the Interpet (white spot still very much in evidence). I plumped for the Protozin - at full strength. Three ingredients seems better than two - the level of formaldehyde seems awfully high in the Interpet treatment - and changing treatments is probably more stressful than repeating the same one; the fish are already quite stressed. Still meant changing 50% of the 280-ish litres of water though
Fingers crossed ... that I made the right choice for zapping the white spot ... and that the shrimps are ok
