Thanks for a nice report. Although it does not contain formaldehyde=formalin (presumably), it contains other proprietary aldehydes. It well may be that their proprietary blend is superior. It may also be a marketing ploy... as old as the ages.
It appears to be the equivalent of Cordon's Rid-Ich that's available in the States and many other blends of Malachite Green and formaldehyde in one form or another.
Why better at night? Are you hinting at the light-fastness of Malachite Green (MG)? It is indeed a chemically unstable, relatively short-lived dye whose decomposition occurs much faster in light but I was never sure if light is NOT an ingredient in its mode of action.
The directions on any MG-containing bottles I have encountered never talk about an application in light versus dark... which, truthfully, puzzled me since I knew about its light-related instability. So, I was never sure what's the best or if both are equally efficient. One thing is rather certain: in the absence of light, MG will remain undecomposed in solution longer. The less light and the less UV light, the longer it will stay around. But again, IDK if this is good or bad or neutral...
In reference to what's below: Bacterial and Viral action also surprises me. Anti-parasitic and anti-fungal properties I understand... but it may be that they aim to make it sound like it is a panacea, going back to the ploy
The description from the manufacturer: http://www.seachem.com/Products/product ... Guard.html
ParaGuard™ is the only fish and filter safe aldehyde based (10% by weight) parasite control product available. Unlike highly toxic and difficult to use formalin based medications, ParaGuard™ contains no formaldehyde or methanol and will not alter pH. ParaGuard™ employs a proprietary, synergistic blend of aldehydes, malachite green, and fish protective polymers that effectively and efficiently eradicates many ectoparasites on fish (e.g. ich, etc.) and external fungal/bacterial/viral lesions (e.g., fin rot). It is particularly useful in hospital and receiving tanks for new fish and whenever new fish are introduced to a community tank. For use in freshwater or marine.
Sizes: 100 mL, 250 mL, 500 mL, 2 L, 4 L, 20 L
Types of Infection Treated: Parasitic, Fungal, Bacterial, Viral
Directions: In the aquarium, use 5 mL (1 capful) to every 40 L (10 gallons*). Repeat daily as required as long as fish show no stress. For 1 hour dips, use 3 mL per 4 L (1 gallon*). Dips may be extended if fish show no evidence of stress.