UV Clarifier vs Beneficial Bacteria: Which Clears Water?
UV clarifier vs beneficial bacteria compared: green water, string algae, how each works, running cost and which fixes your problem.
The short version
A UV clarifier kills suspended single-celled algae, which is what green water is, and it works within days. Beneficial bacteria compete for the nutrients that feed algae and improve biological processing, which works slowly and addresses the cause. Use UV to clear green water now; use bacteria to keep it from coming back, and understand that neither touches string algae.
At a glance
| Flexzion 55W UV Pond Clarifier | Aquascape Dry Beneficial Bacteria | |
|---|---|---|
| Clears green water | Yes, quickly | Slowly, indirectly |
| Affects string algae | No | No |
| Addresses the cause | No | Yes, nutrient competition |
| Ongoing cost | Electricity and bulb replacement | Repeat dosing |
| Works immediately | Within days | Over weeks |
| Harms filter bacteria | No, they live on surfaces | No |
Choose the Flexzion 55W UV Pond Clarifier if…
The pond is pea soup and you want to see the fish again. UV is the only thing that reliably fixes suspended algae quickly, and it does not harm the beneficial bacteria in your filter because those live on surfaces rather than floating past the lamp.
Check Flexzion 55W UV Pond Clarifier on Amazon
Choose the Aquascape Dry Beneficial Bacteria if…
The water is clear and you want it to stay that way, or you are recovering after a clean-out. Bacteria address the nutrient load that causes the problem, which UV never does.
Check Aquascape Dry Beneficial Bacteria on Amazon
We also have full reviews of each: The Pond Guy UltraUV 18 watt review and Aquascape UltraKlean 3500 review.
Related
Comparison based on published manufacturer specifications and the general consensus of owner reports. We have not tested these products side by side. Confirm current specifications and prices before buying. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.
Frequently Asked Questions
Why does UV not kill string algae?
Because string algae grows attached to surfaces and never passes through the lamp. UV only affects what flows through it, which is why it works on suspended green water and does nothing for the stuff clinging to your rocks.
How often do UV bulbs need replacing?
Typically annually, even though the lamp still lights. Output falls well before the bulb fails, so a lamp that looks fine can be doing very little. Note the date when you fit it.
What actually causes green water?
Excess nutrients plus sunlight, usually from overfeeding, overstocking or too few plants. Fixing those is the durable answer; UV manages the symptom while you do.
Planning or running a pond?
Use our free calculators and guides to get every number right.
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