Brown Algae - UV Sterilizer?

Hey there! I have been starting to see brown algae in my tank and i'd like to keep it from getting out of control. I am fairly certain its diatoms, as it comes off surfaces easily. I was considering a UV sterilizer and wondering if that solution has been effective for others.

Tank Info:

• 45 gallon
• Fluval Aquasky 2.0 LED lighting
• 6 threadfin rainbowfish, 4 red phantom tetras, 2 dwarf gourami, 2 lyretail swordtails, 2 mystery snail
• Planted with anacharis, el nino fern, and Alternathera reineckii
• PH 7.6, Ammonia 0, Nitrates 0

Side note, my alternathera is not exactly thriving, which I suspect is because it requires more light than my Fluval is providing. Anyone else growing this? Tips?

Thanks in advance!

First, a UV sterilizer will not control any form of surface algae (meaning, algae that grows on surfaces in the aquarium). UV does help with green water which is caused by unicellular algae that floats in the water, though this is not exactly thorough due to the circulation of the water mixing before/after it has run through the UV. But UV will not help with diatoms.

Diatoms occur when the system is unbalanced as frequently occurs during the first couple of months of a new aquarium. Once the system is balanced, this should disappear. Diatoms can also appear at other times, caused then by another imbalance of light and nutrients (really the same thing, only here from more specific factors). It is more common in lower light than higher, and nutrients have to be present to feed it. Organics from the fish and their feeding are the nutrient sources, though plant fertilizers can add to this. Keep the substrate clean, do 50-70% weekly water changes (this volume at each), keep the filter clean. Organics can readily build up in these areas.

Silicates present in the source water can aslso be a problem with diatoms.

I realize it won't help with whats on the surface (all of that needs wiped off and cleaned manually), but i've read it will help for anything free-floating.

Would something like Phosguard help with silicates?

FreshPaige said:

I realize it won't help with whats on the surface (all of that needs wiped off and cleaned manually), but i've read it will help for anything free-floating.

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No, UV is no benefit because the algae attaching to objects has more than enough space to reproduce without going anywhere near the UV.

FreshPaige said:

Would something like Phosguard help with silicates?

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Before even considering this, I would want to eradicate all other possibles. Chemical filtration is not advisable in planted tanks.

But I just thought of something...you are sure this is diatoms and not the dark brown form of brush/beard algae? If it comes off very easily with your fingertips it is likely diatoms; if not, it is not diatoms.

FreshPaige said:

Side note, my alternathera is not exactly thriving, which I suspect is because it requires more light than my Fluval is providing. Anyone else growing this? Tips?

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Just noticed I missed this question previously, sorry. Yes, Alternathera requires strong light, and light high in the red spectrum. Aquatic plants need red and blue light to drive photosynthesis. The colour of the leaves is due to the light the plants reflect, so red-leaf plants are reflecting a lot of red light, which means they need even more of this for photosynthesis. Light intensity is important (as for all stem plants as they are faster growing thus requiring more light) but it must have a high level of red.

I know nothing about the mentioned light, but see if you can find spectrum data. LED is often higher in blue with less red, unless it is specifically designed for freshwater plant tanks. Every LED I have tried lacked sufficient red, but I've no experience with this fixture.

The algae comes off very easily with fingertips. Thanks for all your input here. I'll keep on with the water changes and keep on top of the nutrients.

The Fluval is marketed for planted tanks with low and mid light needs; sound like its falling short for plants like Alternathera. I didn't know anything about the plant when I bought it (had an "ooo pretty!" moment at the LFS and didn't think it thru). I have the red and blue cranked all the way up on the light hoping for the best, but they look...meh.

FreshPaige said:

The algae comes off very easily with fingertips. Thanks for all your input here. I'll keep on with the water changes and keep on top of the nutrients.

The Fluval is marketed for planted tanks with low and mid light needs; sound like its falling short for plants like Alternathera. I didn't know anything about the plant when I bought it (had an "ooo pretty!" moment at the LFS and didn't think it thru). I have the red and blue cranked all the way up on the light hoping for the best, but they look...meh.

Click to expand...

Yes, from the sounds of it the light is not going to be sufficient for this plant, so fine, move on to another. Over 30 years I have tried many plants; if they manage under my light, fine; if not, I toss them and try another. Our aquaria are very artificial when it comes to plants; no where in nature would you ever see the combinations we expect. Plants share similar needs with certain other species, just as fish do, and keeping plant/fish that have those particular requirements is key to success.