that's a beastly LED!
395nm is a bit low in the spectrum for ionizing radiation, it's more in the dental blue / royal blue spectra AKA "black light". I'm sure it works great for lighting up scorpions, white clothing and posters from the 60s :)
germicidal led are hard to come by, getting such a narrow bandgap (100-250nm) is tricky in conventional semiconductors, so they use more exotic stuff and that means $$$$
cheapest way to sterilize water on a budget is with a germicidal fluorescent bulb. made from special glass that does not block the short-wave UV. Put it straight into the fresh tank and it'll kill cooties day and night, and keep the tank from freezing :)
Ultraviolet radiation
