Algae ID please

I'm hoping someone will be able to help me ID my mystery algae.

This algae ranges in color from light green to dark green, and in some areas it has turned almost a rust color (though the rust colored areas do not seem indicative of dying patches). It feels gelatinous, soft, and slimy as slimy gets. Its filaments look like fine strings of green beads - visible in the picture - and they move like anemone tentacles in the current.

I've had this for some time now, letting it grow out for a better ID match. It only seems to be growing on the wood hardscape and filter parts... not bothering even my most algae-susceptible plants.

The tank it's in is well established and heavily planted. The only other algae issue is some spot algae that periodically appears on the glass and damaged foliage.

I've referenced the Aquarium Algae ID blogspot as suggested in other algae ID threads and did not find a match.

 

I haven't been able to find any good photos of Maiden's Hair, so I'm not sure how the two compare. I would agree, however, that the mystery algae is something I'd expect to see in a SW aquarium. No SW is in proximity to this tank, and I assure you that the algae is having no difficulties thriving in my freshwater tank!

Any other suggestions?

 

Freshwater Cladophora species, as I understand it, are normally coarse in texture and more hair-like in structure. Also, I don't think I've ever heard of a freshwater Cladophora descibed as 'slimy'.

The tank gets weekly 40% water changes, and is dosed after each one with the Tropica Plant Nutrition solution. I am also using pressurized CO2.

 

I've looked through [what I think are] all the clado photos at algaebase.org and I still don't think I found a match - though some of the photos did not show too much detail, so it might have been in there.

Until I figure out it's true identity, and based on my observations of its growth in my tank (see first post), is this likely an undesirable algae?

Here's a couple more shots from today:

 

I am wondering of this is, in fact, some kind of cyanobacteria.

Thank you Wikipedia for this site on cyanobacteria. Without a macro lens or an electron microscope, it's hard to say for sure, but the mystery algae's filaments look similar to the strings of vegetative cells discussed in the Cell Types section. Whether or not small variances in these vegetative cells (if that is what they are) - which I think I can barely detect by eye - represent akinetes and heterocysts, I don't know.

The site also mentions that the cyanobacteria color morphs range from blue-green to rust to black.

Picture excrpt from above site:


Finger shot - out of water:

 

I think this is looking too complex a structure to be a cyanobacteria now...

I've been able to get some pictures of it under a scope.

 

Oh ho! I think you are on to something with the Batrachospermum sp.

I am going to dig around for more info on this and report back...

 

Well, from the pictures and very short descriptions I've found for various Batrachospermum species online, I think my mystery algae lines up.

However, Batrachospermum info seems quite scarce online! Can anyone give me a rundown on this algae? Any observations of it in aquariums? I suspect one might find some info on Batrachospermum (also known as freshwater 'red algae', I understand) in a freshwater algae text...

 

Thanks Tom.

I find it strange that this algae would be so rare in aquariums given that the preferred conditions you described are not unusual.

The 90g it's in gets 4WPG of compact fluorescent light (the red algae gets direct light) and the lights are on for 10/day. The only filter on it is an Eheim 2217 which produces a fairly good current when the plants aren't completely overgrown. I do weekly 35-40% water changes and dose Tropica Plant Nutrition and pressurized CO2. It's basically a shrimp-only tank and I wouldn't expect any of the inhabitants to eat this algae. The only aeration - of oxygen - comes from the plants and what little exchange occurs via surface movement; the water surface is never broken by bubblers or other power heads/filters so that as much as possible of the dissolved CO2 is retained. Temperature is normally between 74.5F and 75.5F.

I can't think of any other parameters that would make the environment unique...

It may be worth noting that the CF bulbs have not been changed for a couple years. I've been putting that off because I'd like to replace my CF lamp with a T5-HO lamp (haven't decided yet between 2.4WPG or 3.6WPG with the T5-HOs). Do you think that change might adversely affect the red algae?

Since this algae is quite pretty indeed (and saves me the trouble of attaching moss to the places the algae is already growing) and is in no way bothering any of my other plants, I'd like to figure out what property/properties of the tank which it likes so much so I can keep it happily growing.

Thanks for all the input everyone - I'm very excited about this algae in my tank (gosh, how often can you say that?)!