Nice pics! In your opinion, what is the most common reason for black spot algae?

 

I am unsure what causes black spot algae I've only had it once or twice. I just have a microscope with camera attachment and thought it would be useful to future people to take photos of the algae microscopically. Maybe it will be helpful to the hobby when figuring out what we have and how to treat it?

I am not even fully convinced that increasing phosphates kill off green spot algae.

I think green spot might be black spot algae. I couldn't quite tell from the microscope pics since the green spot algae was pretty small compared to the black but you can see green and black growing in the same area in the color photographs, they are intermingled (top right picture). I wonder if unhealthy green algae is actually black algae? What do you think?

The one thing I've noticed after Jeffy analyzed my water is that my K is low (but my PO4 is 2.5 ppm and my CO2 is high). There were a couple of threads a few years ago about how low K can inhibit PO4 uptake, so perhaps my low K values are causing the algae to change color.

It might be that the black colored spot algae is actually a deficiency sign in algae of some nutrient (presumably K deficiency?). The cells look more swollen than the green spot, so perhaps it is having issues.

 

I am unsure what causes black spot algae I've only had it once or twice. I just have a microscope with camera attachment and thought it would be useful to future people to take photos of the algae microscopically.

I have one tank that gets it routinely on the slower growing Anubias, another tank with same conditions, that doesn't get it. Have never figured out why.

I am not even fully convinced that increasing phosphates kill off green spot algae.

Agree, completely. A lot of the so called 'knowns and tenets' of algae/fertilization, etc, I quit believing long ago. I am one of those who believes that while there certainly are 'generalities', there are no 'certainties'. There is just too much variation from water source to water source, not to mention all the other variables coming from people's lighting, filters, flow, substrates, feeding, fish, etc....

I like the pics you're posting. I'll look forward to follow ups, if you're successful in dealing with these, on how you did it.

 

Well an interesting turn of events...

Due to some of the data in JeffyFunk's water tests I decided to add more iron to my tank to see if it has an effect on BBA and I found that the black spot algae turned bright red within a few hours of dosing iron. A few articles I've been reading also suggest that high iron levels might be toxic to certain species of algae and plant so I figured I'd give it a try and see what happened.

I did my usual 50% water change last night and added the normal 8.5 g KNO3, 0.6 g KH2PO4, 3 g K2SO4, 0.6 g CSM+B and decided to add 8 grams of 11% DTPA iron. I used the fertilator to calculate that this should have added roughly 1.6 ppm iron to my water maybe a little more (the fertilator only has 10% DTPA iron not 11% like I used). The iron dose made the tank water look greenish-yellow and it still looks like that today.

Anyway, here is the black spot algae (same algae as in the top right picture):

And I also noticed that my R. macrandra red and Green have curled new leaves which weren't there yesterday. I will see if this gets worse or is a trivial effect of the high iron doses.

Oh and one more thing, I found a fantastic guide to identifying freshwater algae, the book has many microscopic photographs and descriptions towards the end of the book.

Algae ID book:​

Freshwater Algae : Identification and Use as Bioindicators
Bellinger, Edward Sigee, David D.
Pages: 285
Publisher: Wiley
Location: Hoboken, NJ, USA
Date Published: 04/2010
Language: en
LC Call Number: QK570.25 -- .B45 2010eb
eISBN: 9780470689561
pISBN: 9780470058145​

 

Interesting! I've always had trouble with my Rotala. It is curled like yours and also sometimes stunts. I always thought it was my water, i.e. to hard. My organics results showed really high fe. Maybe that's part of my issue?

I also have tons of green spot algae and what I thought were diatoms. Now I think its actually black spot algae. Just doesn't seem like diatoms.

Thanks for posting this, it really gets me thinking!

 

No problem. It was actually your results that got me thinking about high iron levels. You have 2.7 ppm iron and no BBA. What chemical are you using to add iron? Can you take macro photos of the Rotalas and the algae?

Also, I think the red color in the above photo means it is dying, not growing well. But it has only been 12 hours since I dosed the high iron so we will have to wait and see if it dies off or what.

 

Just an input, it seems that my Rotala Macrandra also curls its leaves when it is neglected of light...

 

I've got my Macrandra grown all the way up to the surface in a 20" tall with quad t5ho...putting me at about 4.7 wpg. The Macrandra when first bought from the LFS was a deep red, after a few weeks i'm noticing that new growth is curled like the above pics.

My tank is also showing some crazy GSA not only on the glass, but i've noticed my healthy Anubias with GSA on the leaves too. I've been incrementally moving the lights up to stop the progress of GSA, only to notice that the macrandra is fading too.

If it helps, i've been dosing 3ml of iron, ppm of .33 in a 20 gallon tank, and i have been dosing 2ppm of KH2PO4 & 10 PPM of KNO3. The only thing i've noticed with the addition of KH2PO4 & KNO3 is more compact growth...but coloration has not changed.

If i wanted the 'deep red' back in the Macrandra i suppose i could lower the lights back down to 3" above the water...but i don't want the GSA to go crazy again. As it stands, i'm still in the process of raising the lights to halt the growth of not only GSA, but BBA and Hair too.

 

Interesting. If it does turn out that high iron levels are a deterrent for other nutrients to be taken up this would actually make a case for using iron sources with weaker chelators or none at all such as ferrous gluconate.

I'm thinking of Tim Gross' tank where he is adding 1.25 ppm / day of iron via Flourish Comprehensive and Flourish Iron, yet his iron readings are .03 ppm in the water column. He has no issues with curling new leaves.

I was dosing considerably less than that at maybe 0.3 ppm / day of iron in the form of DTPA and my iron levels are 1.15 ppm in my tank and I do struggle with curling new leaves.

Maybe all those chelators aren't a good thing afterall?

 

Iron might be usable as an algae inhibitor. If it does work as a deterrent it works because it is toxic to the algae at higher levels.

The strange thing is, I read a few papers that seem to be saying non chelated iron (dosed at 1.125 ppm as FeCl3) was toxic to duckweed and turned it yellow after a few days.

We don't use FeCl3 obviously but I wonder if the curling leaves you and I saw is due to a toxicity as well. I think it is. I noticed some plants going yellowish and curling the day after I dosed the 1.6-1.8 ppm DTPA iron.

The algae didn't die off completely after it turned red. Presumably that is because iron levels must have dropped as the plants took it up and so the toxic concentration of iron didn't stick around long enough to kill it all off. Though the red color is definitely an indicator that it was unhappy. I wonder if a lower level of iron would do the same thing but spare the plants leaf curling and yellowing.

I don't think it is the chelators causing issues they are not toxic as far as I know, they help to decrease the toxicity of heavy metals. Other studies I have read show that you can dose anywhere up to 10-20x higher of some heavy metals (like copper) if they are chelated without seeing toxicity symptoms.

I'm not sure exactly why some forms of iron do not show up in tests and other forms do in our aquariums.

In natural systems there are a number of ways iron is removed from the water column. H2S can quickly remove it and make it precipitate out. Bacterial films also remove it under anaerobic environments.

Iron can also be bound up by organics in the water. Organics tend to bind a lot of heavy metals and make them unusable, the research I've been reading notes this happens for several different metals. So perhaps in our tanks organics play a larger role than we think.

You know it is funny, but freemann (not sure if you remember him from a few years back), he used to dose a lot of iron regularly because his plants were always slightly yellow and he figured the plants were iron deficient so he kept adding more iron. I recently read that iron toxicity blocks sulfur uptake. Sulfur deficiency is characterized by whole plant yellowing - which looks very similar to iron deficiency. So I wonder if what he was seeing as iron deficiency was in fact an iron toxicity which caused a sulfur deficiency (and that was the yellowing he was seeing).

I think dosing very high levels of iron is not without its risks. I don't think I'd recommend having over 0.5 - 1 ppm in a tank at any given point. Obviously the toxicity depends on organics, the type of iron used, and plants involved so I suppose there is some degree of wiggle room.

 

Wow! Another great thread Zapins, subscribed! And off course testing this one myself with Easylife Ferro. Not sure what the chelator is but I think I can find out. Perhaps I'll try it in my barely planted Vietnamese biotope, which is always covered in different types of algae (intended) and lots of BBA (unintended )

 

It's nice to have a good group of people on APC who are enthusiastic about testing out the finer details of planted tanks Yo-han. I just so happen to have access to a microscope and good camera so I do my part when I can.

I also wouldn't mind fleshing this theory out a bit more with further tests. I got the idea from the data from Jeffy's Organics thread.

The sample: BM Aq 10/17/13 had 2.7 ppm Fe and no BBA even though there were high organics in his tank water (which we think is the trigger for BBA). I later researched iron toxicity values and it seems like 2.7 ppm is well into the toxic range if non-chelated iron is used (not sure what value is toxic for chelated iron - but perhaps it is similar?). His values were the anomaly in the entire data set. So I added iron to my tank to see if it did anything to black spot and it seemed to, along with the yellowing and curling of the plant leaves.

The DTPA iron discolored the water an orange/yellow color which wasn't really visually appealing. Does the ferrous gluconate iron or the flourish iron discolor the water when dosed?

 

If you dose according to above recommended, then no, here is no water discoloration. I dose Flourish Iron and don't notice any difference when dosing 1-4ml in a 20 gallon.

 

Hmmm...this is interesting to me too. I was dosing DTPA and got some Glut for free so dosed it and had a noticeable change in my plants. So ive kept dosing both. Maybe ill back off the DTPA because I also get some curling issues. Ive also heard some of the older group say Fe isnt what it used to be but I dont really have any insight as to whether the cheleators are cheap or done differently than they used to be.

 

Hmmm, maybe I should dose a high iron on my nana and sword since those two plant are cover in bsa.

 

Marcel that is quite true. When I was looking at the green spot algae I did see several different shapes of algae under the scope. The black spot algae was much more uniform as you can see by the photos.

Most of the green spot algae was not visible at the magnification I used, it was too small or perhaps it was just completely stuck together to see clearly.

I would find it interesting to see photos of your algae if you want to start a new thread with them. Perhaps I can post more microscopic photos of algae. It would be interesting if what we all know as BBA, hair algae, cyano, etc... look the same under the microscope or if we all have completely different algae species that all happen to look similar macroscopically.

Let us know Window7 I'd be interested.

I need to post an updated picture of the black spot. It seems to have died back a bit on the leaf above after turning red (decayed away?).

 

Mine looks exactly like what you call Black Spot Algae.

It will turn red in contact with a mild dose of H2O2 (too concentrated
and it will qukckly turn light brown) or when I use ozone.
After that it will turn pale green and light brown before disintegrating.
Or back to normal if the damage is not seious enough.

I think it is cyanobacteria, from its smell.

 

Found a paper that mentions how DTPA iron does not degrade significantly over 24 hours in water.

The present study assessed the stability of uncomplexed DTPA and Fe(III)-DTPA over 24 h, under experimental conditions similar to those previously used to assess the aquatic toxicity of DTPA and Fe(III)-DTPA (MS synthetic medium, 20°C; wet laboratory water (WLW), 25°C). DTPA was measured using ion-interaction reversed-phase liquid chromatography at 0 h (t0) and 24 h (t24). DTPA consistently eluted at approximately 3.3 min. Actual DTPA concentrations corresponded well with nominal concentrations, justifying the use of nominal concentrations for previous ecotoxicological bioassays. There was no significant degradation of DTPA either when uncomplexed or ferric-complexed, over 24 h (P>0.05). In addition, there was no difference in DTPA and Fe(III)-DTPA degradation between MS synthetic medium and WLW (P>0.05). Therefore, the previously reported decrease in DTPA toxicity, when complexed with iron was concluded not to be due to enhanced DTPA degradation. However, the presence of what appeared to be a degradation product in all Fe(III)-DTPA samples after 24 h, indicated that DTPA might be more susceptible to degradation when complexed with iron, as reported by other researchers.

From:​

R.A van Dam, N.A Porter, J.T Ahokas, D.A Holdway, Stability of DTPA and iron(III)-DTPA under laboratory ecotoxicological conditions, Water Research, Volume 33, Issue 5, April 1999, Pages 1320-1324, ISSN 0043-1354, http://dx.doi.org/10.1016/S0043-1354(98)00332-7.
(http://www.sciencedirect.com/science/article/pii/S0043135498003327)​