ncje

I was silly enough to change out one of my tubes for a blue light about 2 months ago. Have to say the fish look great under it, so if I was stocking only african cichlids with lots of rock formations and NO PLANTS it would work great. But plants dont like it, more to the point algae loves it. So not long after you will have a bloom of algae on every plant in your tank. Now I regularly check my readings, actually once a week before and after my water change. There has never been more than a slight up or down in nitrates which are usually around the very low end of around 5ppm, NEVER anything for amonia or nitrate.

Anyway the problem with this algae is it grows on every surface including your plants, and gets so thick your plants struggle for any light at all. Of course Ive changed it out now and replanted my pots with six beautiful amazon swords. I still have some original plants that are struggling but now are starting to come back. So with plants, no blue colored lights.

Isabella

What type of algae are you getting?

And it's all true. Blue light tends to cause a lot of algae and plants really don't like it. Now listen to this (this is what I've learned on Plant Geek): if you have a planted tank, you actually need some nitrate in it (around 5 - 20ppm). This is because nitrate is an important plant nutrient, and if plants don't get all the nutrients they need, they start to die and to decay. The decaying leaves are food for algae. And this is how you can get a lot of algae when you have even 0 nitrate! Interesting, huh? Now, if plants don't like the blue light, they also won't grow well under it. So they start to decay ... and hello algae!

In my 10 gallon tank, I have a light that is slightly bluish and there is 0 nitrate at all times. Guess what? I have tons of blue-green algae in that tank. In my 30 gallon tank, I have a natural light (looks like daylight) and nitrate around 5-10 ... and NO ALGAE in there. However, this may be due to the algae eater that I have in there. He will eat all algae EXCEPT the black brush algae. And I do have some black brush algae in the 30 gallon tank.

ncje

Well after a week the Amazon swords are doing great. Already showing some solid growth and not one drop of algae. The other plants are showing some signs of recovery also.

Butterfly

Are you using moonlights? If so they are only suppose to be used for short periods of time to view your fish at night after you turn your other lights out. That short period of time shouldn't cause a problem.
Carol

Isabella

Carol, are you saying that prolonged periods of moon light may cause algae too?

Butterfly

I would imagine if left on for prolonged periods of time it might encourage algae. Is this not the kind of blue lights you two are talking about?
Carol

Isabella

Well, I think there is a large difference between normal actinic blue lighting (which has wattage as a normal fluorescent or compact fluorescent bulb) and a blue moonlight (which has only a few watts of light, if not something around 1 watt). Unless you have some different moonlight in mind, I don't think a moonlight of 1W or so should cause algal blooms even if left on for an entire night. BUT, this is only what I think, not something I have read for a fact, so I may be wrong. It just really seems highly unlikely to me that any light as low as 1W (left on during the night) can cause algae.

Butterfly

Gotcha, sorry I didn't understand what kind of blue lights you were speaking of
Carol

Isabella

It's OK!

eldo

i have a 55 gallon tank with freshwater fish it came with an ultraviolet light do you mean this also is not good

Isabella

Ultraviolet light? I think maybe you mean actinic blue?

Tamara

i was just reading this on how it makes algea...
well is it the type of algea that plecos just might like?
because there isn't much algea at all in my tank anymore and i feed him lettuce, avocado and cucumber.
but i find he likes algea much more.
+i only have fake plants.