Do I really need an UV filter for a planted tank?

**Filet-O-Fish** · 23rd Jul 2015, 12:19

Hi Guys,

For the past 1 year, I'm running an EHEIM reeflexUV 800 UV filter in 300 Lt planted tank. It works with a timer attached for 11 hours (6pm to 5am). This UV unit is rated for 400 Lt to 800 Lt tank volume.
I bought this UV unit before I even bought the tank with the hope that I can keep parasites and algae at bay ( a victim of all those YouTube propaganda on UV)

But now I question the usefulness of having a UV filter.
Currently my tank has so many types of algae ( although in small patches on the substrate, glass walls & wood scape). You can find GBA, Diatoms, BBA, GSA, GDA in my tank.

The only thing I have not experienced is health issues for my fish through but then again, it might not be the UV that's helping but the many plants in the tank that's soaking up all the ammonia and other stuff.

Maybe UV filters are not a necessity for a planted tank but a must have for fish only tank which produces lots of waste in the tank?

What do the members here have to say about UV filters? Would the algae issues in my tank be more serious if not for the UV unit or am I just under the "placebo effect"?

Please share. Thanks.

**reeshee** · 23rd Jul 2015, 22:34

The effectiveness of UV light is usually 6-8 months for me. After that, i'll go to LFS to buy a new bulb. Maybe you are due to replace your bulb? Also, it only kills stuff in the water and not on the tank walls, plants, rocks and stuff.. So your water should be crystal clear but not necessarily your items in the aquarium.

Personally, for me, it helps. I wouldnt stop using a UV sterilizer. I keep my aquarium outdoors in my patio and I get sunlight but no green water.. and minimal algae which is easily wiped off during weekly WC.

Good that your fishes are doing well!

**Urban Aquaria** · 23rd Jul 2015, 23:51

Of all the algae types you mentioned, i don't see green water as one of them, so it means your UV sterilizer is working to keep suspended green algae and spores at bay.... for the rest of the other algae types, they attach and grow on objects, so the UV sterilizer doesn't do much to affect them.

In some cases, it could also be the suppression of one algae type (ie. green water) which allows other algae types (ie. hair/thread algae) to flourish. Something has to use the excess light and nutrients, so its just a matter of which is allowed to be dominant. That's one of the reason why in outdoor ponds with thick mats of hair algae, the water is super clear, because they soak up all the nutrients and block light from the green water.

For freshwater planted tanks, while most people would say that having healthy fast growing plants can out-compete algae (something thats easier said than done

), i guess it can still be good to have a UV sterilizer running to reduce bacterial counts and suspended algae spores in the water column, which can offer some general benefits to the health of tank livestock.

Outdoor ponds utilize UV sterilizers because its usually the most common way to help manage various issues that plague outdoor setups (ie. green water), especially with exposure to sunlight and with high-bio load livestock, ponds need all the help they can get to fight the uphill battle. On the other-hand, with indoor planted tanks we can control much more of the inputs and parameters, hence not so crucial for additional equipment like UV sterilizers.

**IrvineChen** · 24th Jul 2015, 06:52

UV sterilizer plus algae exit.. and good bye to all algae in yr tank... and with a little help from your clean up crew.. it will be awesome.. else can spot treat with Excel or hydrogen peroxide to have a final excellent finishing..

**ronald_t80** · 24th Jul 2015, 10:19

Originally Posted by IrvineChen

UV sterilizer plus algae exit.. and good bye to all algae in yr tank... and with a little help from your clean up crew.. it will be awesome.. else can spot treat with Excel or hydrogen peroxide to have a final excellent finishing..

Will Algae Exit harm the faunas inside?