Weird algea

[EXVISOR13]

Hi all ,newbe here
I at one time was doing corals and I had this thick pretty green algea growing on my glass ,I would only clean the front glass and leave the other alone as it was neat looking and growing
I decided to take a break from corals for a while and i'm just doing fish and live rock
I have a 125 gal tank and all the algea on the glass turned to a purple / brown color and is bubbled up and coming off like bad paint
the only thing that has changed since im not doing corals is the lights are not on as much and I no longer worry about keeping the ph up
is this normal????????
I have been removing it little at a time as it is messy and I try to net what falls off
What's weird is under it is still green algea that I left on the glass that does not want to come off

[Birdlady]

Probably normal. Have you increased the bioload on the tank?

It sounds like cyanobacteria. Icky messy stuff! Due to excess nutrients in the system.

Could you give us a run down on what you have? Tank size and filtration? How many fish and how long has the tank been running...etc

Then maybe we could help a bit more!

Welcome to 3 Reef!

[EXVISOR13]

I have a 125 tank ,about 75/100 live rock, I have 720 watts of lights , combo of pc and vho ,running a wet and dry off a 1600 gph pump as well as two external 400 filters
Also have a skimmer and a chiller, not doing corals right now, only have one fish, a large puffer about 12 inches long

[mmakay]

Lots of light for a fish only tank! No skimmer? I would seriously consider adding a good skimmer. That will do a lot for reducing excess nutrients. Filters are ok if you really keep up with their maintanance, but they can produce lots of nutrient if they get a little dirty. Fish food, fish poo, etc. will just sit in there and decompose making lots of stuff that algae LOVES to eat.

[inwall75]

I'm offering a possible second answer. It sounds to me like dieing coralline algae. I've seen it come off in sheets like they described. There is a lime green coralline that is quite tolerant of light. I suspect that the purple strain took over due to the lower photoperiod but it grew over dead green coralline and fell off when the green died. Just a thought.

[EXVISOR13]

I do have a skimmer, I also tried it with less light as well as with all the lights, does not seem to make a difference, for some reason it starts to grow back on the glass, not so much on the rock as my fish are picking at it and keep the rock clean ,I tried sscraping all of it of down to bare glass ,states out with normal green algea then this purole stuff starts to grow over it, when I remove the purple before it gets out of control I leave the green ,eother way keeps coming back