Rock loving algae - what kind? Should I care?

[Linwood]

I'm getting very slow growth of something on rocks in two different tanks, I think two different things.

Both are growing very slowly, are very low to the rock surface, and do not appear to be (at least in similar form) on any plants or other surfaces.

Both are apparently immune to lots of algae eaters (one tank has SAE, BN Plecos, an otto, and lots and lots of snails, the other the same except for the otto).

Both seem to drink hydrogen peroxide and come back for more -- I inject it over it in still water, it fizzes and foams and gives of lots of white bubbles just as you would expect. And nothing -- for days after it looks the same.

Is it even alage? Or (particularly the green) some kind of moss?

I could remove most of these rocks and sterilize, but especially the green I do not mind so much if it's not in some fashion bad, e.g. if it's not going to spread to plants or glass. In fact it may be GSA, I have that mildly elsewhere, but it's decreasing as I increase phosphate.

The black I'm tempted to sterilize, but would like to know what it is.

Green:

Black (sorry, this is behind a thick bunch of jungle val, can't get a clear shot; the kind of purpleish glow is reflection at this angle from the lights or flash, to the eye it looks black).

 

[Mebbid]

Its algae and theres no need to sterilize... it'll just come back.

How long do you leave your lights on daily?
What light fixture?
What rank size?
What ferts do you use?
What is your carbon source?

 

[Linwood]

There are two tanks, but I treat them similarly. One is 45G and one is 220G, low tech, cycled but fairly new (45G from June, 220G first cycled in September). The 220G is a deep one at 30" with about 3" average substrate.

Both tanks are lit with a Current Satellite LED+, the 45G with one (that's the one with orange rock and black stuff), the 220G with four LED+'s, overlapping for 2' in the center. The rocks with the algae are under the non-overlapped portion (so under 2 lights), and about 12" up from the bottom (so about 16-18" from the lights).

Lights are on for 2 four hour periods per day, with about 15 minutes ramp up/down.

I dose with (large tank - small proportionally):

20ml Flourish comprehensive weekly
10ml phosphate daily (aiming for abou 2ppm)
20ml iron DTPA 10,000ppm mix daily (aiming to sustain 0.1ppm)
20ml Potassium weekly (except one weeks with water changes as I use equilibrium)

No injected CO2, but use 20ml Excel equivalent daily.

The tanks are planted with jungle val, wisteria, crypts wendtii, and a variety of other mostly low light plants, all doing quite well. I had some GSA which has been going away with the introduction of more phosphate.

I had quite a lot of staghorn (plus maybe some hair) algae, but some hungry SAE's took care of that very quickly. The 45G tank has one plant with a bit of BBA that the SAE's do not seem to be after, but it is a tiny amount. No other visible algae (other than those in the photos).

Was hoping for an ID of the type of algae so I could read more about it.

AS to "it will just come back" - it is seriously slow to grow. Unless it gets more rapid, if I remove it I'm talking months to get this far along.