Aquatic Plant Forum banner

Green Thread Algae - what imbalance?

2506 Views 7 Replies 4 Participants Last post by  Seattle_Aquarist
And now it is my turn to battle algae. I have Green Thread Algae overrunning my 12 gl 3-foot tank. The tank is about 6-months old and is about 40% planted with Rotala macrandra and 1 small red tiger lotus. The other 60% are Hemianthus callitrichoides and micranthemum, under 6700K HO H5 39W x 2 lights ~ 8hrs/day, Finnex 360 cannister filter, 100% AquaSoil Africana sand (NO PowerSand), Hagen 88 mini pressurized CO2 kit (grr) at about 25 ppm 24x7, EI-mid-range style fertilization, GH 6, KH 3.

I finally started doing testing and got Ph 5.8, NH3 0ppm, and NO3 of 80ppm (immediate 50% WC + Prime). I did not test PO4 before the WC.

The tank has no visible signs of any other algae, except 3-4 tiny spots of GSA.

I read the Controlled Imbalance thread. Most of it makes intuitive sense to me. Nevertheless, I cannot claim that I understand the tank's current water conditions. Macrandra, I understand' is a Ca priority plant and my NO3 is way over the top as it is. Therefore, I'm leery of starting the NO3 protocol.

Any insight is much appreciated. Thank you.
1 - 8 of 8 Posts

If I get hair/green thread type algae outbreak it is typically during the first month of operation when the tank is going through the "nitrogen cycle". When it happens I usually have a high ammonia, nitrite, or nitrate level.

To combat it I do the following:

1) Manually remove as much as possible

2) 50% water changes 3X per week to reduce nutrients; also it will weaken the algae which cannot adapt to changing H2O conditions as well as higher plants

3) Add Siamese Algae Eaters (SAE); SAE seem to really enjoy a meal of hair/thread algae; 1-2 should do the job in a 20 gallon

4) Reduce photoperiod by 33% until problem subsides (2+ weeks) and then slowly increase watching for additional outbreaks

5) Dosing Excel at the recommended "Initial" dose level (5ml/10 gal) but 2X the recommended Daily dose is also effective.

Let us know how it goes!
See less See more
Also 6.5 watts/gal of T5HO is way high light. Might want to unplug one of those bulbs. Even then you're looking at some potentially high PAR values.

Otherwise - What SA said ... +1 on removal and waterchanges. Prepare yourself mentally for what could be a long siege battle. :fencing: It was for me.

All common sense. I have been removing the stuff daily (gets old after a while). I've been keeping photo period at 6hrs/day for the last 2 weeks. It's an open-top tank and SAE tend to jump :(, so, I'm keeping black mollies there that seem to nibble on the stuff. I'm debating with myself on the light issue: CO2 is close to max and it's a 3-foot long 12 gl tank with all high-light plants. I'm not sure the w/g rule applies here that much.

So, I will follow your advice and start 50% WC every other day and start dumping Excel.

This situation seems like a perfect test lab for trying out the "Controlled Imbalance" approach to algae control, but I'm still leery of adding NO3 to the tank that seems to have more then enough of it already.

Interestingly enough, I had the same problem about 5 years ago in my 75T and 36 corner. It started after I added Rotala Macrandra and allowed it to grow to and float on the surface (beautiful colors). Exactly the same situation as I have now. After ~6 month-long battle, I ended up tearing both tanks apart, down to washing the substrate - could not get rid of the algae otherwise.

Now that I have support of people like you, I would really like to find out what gives with R. Macrandra and whether it introduces nutrient imbalance by being Ca-priority consumer. Identifying the imbalance (if any) and then fixing it is what I am really after.

Any other ideas? Thanks a lot again!
See less See more
According to the Method of Controlled Inbalance, green thread algae is caused by NH3. Since you said that you dose according to the EI method, where did you get your fertilizer from? As I've said in another thread, if you got your fertilizer from GLA, i would check your KNO3 for ammonia/ium contaminations (although any KNO3 source could be contaminated). In my high tech tank, I also suddenly got an outbreak of green thread algae. Looking at my fertilization notes, I was able to determine that the algae outbreak coincided w/ a change in fertilizer. Since then, I bought more KNO3 from and had my green thread algae disappear.
Thank you, JeffyFunk, I saw your prevous post on the subject. All my ferts come from I also tested for NH3 and it's at 0 ppm. Good point worth reiterating, though.
FYI: I stopped fertilization, started dosing Excel 5ml/day and 50% water changes every other day for 10 days. The bloom is gone, the algae is 95% gone.

Glad to hear that you have had substantial success; thank you for the update!
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.