Algae AHH!


New member
Hello. I currently have a 40 gallon tank that holds my Peacock Mantis :rollface: Chucky. I've been having some problems controlling the algae in the tank. Does anyone else have a problem with as well? I seem to have a mix between brown and green algae. The brown algae is normally on the sand bed and the green is on the live rock. I'm not quite sure what kinds they are but they are getting annoying. I do a 20% water change or so every two weeks. Lately, I've been doing 5 gallon water changes once a week. I feed Chucky one or two 0.5-1.0 inch pieces of shrimp every 4-5 days. I regularly mix up his diet by switching off between 2in silver dales, the shrimp, two half clam shells, and 2 snails or hermet crabs. I'm not quite sure if I'm feeding him too much. Every 4-5 days he greets me by coming out of his den every time I walk into the room. He only peaks his head out for a few days from the time he gets fed. I don't know if hes just not eating the food or if its something else that is causing the algae.

My setup:
40 Gallon
CPR Aquatic Bak-Pak 2 Dual protein skimmer (One side hasn't been working properly for the past 6 months. Doesn't work) Hangs on the side of the tank. Have a fairly large bag of carbon in the skimmer.
150 metal halide with 2x65 actinics
No sump, no refuge
I use a reverse osmosis system to make my saltwater and to decrease salinity.
I have a 3in starfish that sifts through the sand. Hes been there for a 6 months.
Big thing of chato just sitting in my tank (grows like crazy).
Couple corals that were moved to Chucky's tank due to bad water quality in my brothers 55 gallon coral tank.

Would be appreciated if anyone had any suggestions or tips for this algae problem. Thanks!

Here's a video of Chucky and the Tank. I apologize for my relatives commentary haha

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New member
Algae means a young cycling tank or excess nutrients. If you post pictures of it, will try to id. (video won't play for me, says it's private). How are your phosphate and nitrate levels? Sometimes phosphates leach out of rocks for a while and running a phosphate remover helps.

Also, that's a lot of light for a Peacock; do corals in tank require it? Running 48 hours no light followed by interrupted light cycles (i.e. instead of 8 hours light, do 4 hr. light-1 hr. dark-4 hr. light) will usually take care of most filamentous algae. But the excess nutrient problem will persist. Are you harvesting some of the Chaeto out of system periodically? That should help moving some nutrients out of tank.


New member
IMO..I think you have a water quality issue. First....I would test for nitrate and phosphate, but I think your problem might be with your RO water. Optimally your RO should be at 0. Your changing a good amount of water and if it's full of TDS then your just feeding the algae. If you don't have a TDS meter you could take a sample of the RO water to your LFS for them to test. you have a sufficient clean-up crew in the tank? You did mention a 3" starfish, but you need more then that. I know your peacock will desimate them, but I think it will help.
You might also think about getting rid of the broken skimmer and replacing it, or going with a HOB refugium, a converted HOB filter like the aquaclear 110 could work also. A little live sand, rubble, and that ball of chaeto will go a long way towards helping clean that water up. Good luck and keep us posted


New member
I run granulated ferric hydroxide (commonly called "GFO") phosphate remover in a fluidized bed with my peacock mantis with no ill effects. This might help you.

Make sure you are not raising your water temperature too high, this promotes algae growth. The MH light with no chiller on this small tank may well be raising your temp too high.

Alkalinity should be at 3.5-4 meq/l to reduce algae growth.



New member
Here are some pictures of the tank and the algae


I tried some of the suggestions today. We'll see how they do. I put another pump in to create more flow. I only had one pump pushing around the water. I went out and got a few snails and hermet crabs. Chucky already killed one of them haha.
The temperature seems to drop down to 77 degrees C at night and hits a maximum of 80-81 during the day. I have the light set for 12 hrs on, 12 off.
As soon as im able to find the testing kit, I'll be testing for my nitrate and phosphate levels. Last time I checked ( 4 months ago), they were at zero or close to zero and I still had this algae problem. We'll see what it is now. I do plan to get a phosphate remover to see if that helps.
I've gotta do some calling around, but i'll see if I can test my RO water.
As for the protein skimmer, I hope to get one soon. Not sure which one to get though. I'll do some research.

Thanks so much for the suggestions and tips. Much appreciated. I'll get started on some of the stuff and see I can get this algae problem under control.


New member
Looks like a combination of cyanobacteria and possibly bryopsis. Some notes:

- The algae may well be scavanging available phosphate and nitrate, so your levels may well be zero.

- Try reducing light levels sharply. Like, turn off the MH for a few weeks. That will help a lot.

- Try keeping water temps at or below 78.

Why is the water so cloudy? I think you have some major water chemistry issues. A better skimmer will help, as will some mechanical filtration (like PolyFilter).

Note that if your chaeto is growing quickly, so will your algae. You want conditions in which your chaeto grows slowly...

Please post all of your water stats for more assistance (calcium, alkalinity, pH, nitrate, nitrite, ammonia, phosphate).



New member
Also, cutting back on your light schedule wouldn't hurt. Taking it back to 8-10 hours of light, in addition to some of the previous suggestions, would help.