Decision essentials
Key points
Lamp power is not the delivered microbial dose.
Particles can shield organisms from radiation.
Clearing green water does not prove every pathogen is controlled.
Filtration
Dose is intensity over exposure
Higher flow commonly reduces contact time. Water transmission, chamber geometry, sleeve deposits and lamp ageing all change delivered exposure, so a wattage-only comparison is incomplete.
UVC can injure eyes and skin. Operate only inside the closed housing with its safety instructions and never look at an energised germicidal lamp.
Filtration
Define the target first
UV may reduce selected suspended microorganisms; it cannot treat life stages attached to fish or surfaces. It also cannot repair crowding, unstable water or disease introduced without quarantine.
Green-water clarification, microbial load reduction and multi-tank biosecurity are different objectives with different dose and turnover needs.
From evidence to action
Decision matrix
| Situation | What to do | Why |
|---|---|---|
| Suspended green water | Correct-dose UV and clean sleeve | Cells circulate through the chamber |
| Visible disease on fish | Obtain target-specific diagnosis | Not every stage is waterborne |
| High particle turbidity | Improve upstream filtration | Shielding reduces exposure |
Check the result
After the adjustment, measure flow under the same conditions and check noise, leaks, waste accumulation and circulation. Record the result; if performance drops again, locate the restriction before changing another part of the system. For “Aquarium UV sterilisers: only the exposed water receives a dose”, use clearing green water does not prove every pathogen is controlled as the final article-specific check.
Evidence
Sources and scope
Sources include institutions, technical studies and manufacturers. Chezur separates established mechanisms from editorial decisions for home aquariums.