Green algae and other question

[kc]

I have a 130 gl tank that has about 2" sand bed. I notice the bottom of the tank has lot of pupple algae which is good...but also the green one. It is hard, same as the pupple one. I am running a phosphate reactor and tested the water that doesn't have any phosphate, nitrate, nitrite. I also clean my skimmer and filter pad twice a month. Do you know how can I get rid of them beside scrape them frequently and where are they come from? I don't have any bio-ball and has some live rock in the sump..
By the way, do you have issue with live rock in the sump? Over period time, there are some small rocks or particles fall off from LR and they got blow into the tank. How can I filter them?

Thanks
KC

 

[MikeS]

Some coralline algaes are green in color as well (I have some in my tank that is a lime green color)...but I'm going to assume we are not dealing with a coralline algae in this case.

It's not uncommon for one to get 0 test readings on nitrate and phosphate and still have it be a problem in the tank. Often, the phosphates and nitrates are being used up quickly by the algaes, leaving the water column reletively free of both. These two are almost always the culprits behind algae blooms, so your best bet is manual removal of the algae to remove the nutrients tied up in them, water changes with RO/DI water, maybe take a look at your feeding routine and cut back on that a bit also.

On the skimmer and pads, I'd be cleaning out the collection cup weekly or more often. Same with the filter pads, I'd be cleaning or replacing them weekly.

MikeS

 

[clayswim]

If the green algae are hard like the purple algae are, it's probably just green coralline. If it is coralline you probably don't have a phosphate problem, as that will inhibit coralline growth.

There are always phosphates in the water though that our hobby tests won't recognize. Even the best tests we use, like Salifert, only test for inorganic phosphate. You can have zero inorganic and have a significant amount of organic. Various things in the tank will convert the two back and forth. The best way to deal with them (if you have a problem) is to clean any detritus out, do water changes to remove any from the water column, and prevent them from entering your tank in the first place. Most of it comes in on the food that we use. Cut back on the food, and/or watch which types you feed.

Clayton