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Discussion Starter · #1 ·
Hi Hopefully someone can help me figure out why I have Black residual on my rocks artificial plants, and I believe on two of my yellow labs. Not all the yellow fish look like they been in a coal pile just the two larger yellow male labs. I have a large mail Kenya who doesn't look as bright, but doesn't show a black coat like the labs. None of the other fish seem to have been affected. Maybe it doesn't show as most of the other fish are some shade of blue. Its a 180 gal mbuna tank. Gravel substrate and Holey Rock. I do weekly 50% water changes so no problems that I know of with water quality. I also have a in line sterilizer, two Fluval Fx6's for filtration. I get a little green algae as I figure some may come from the Spirulina. The black residue washes right off when I clean the rocks and it doesn't seem to hurt the fish. It takes about two weeks to accumulate on the rocks. In addition to the Spirulina I feed Omega one flakes and pellets. Has anyone had this residue problem? Thanks for all thoughts
 

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Throwing this out there see what you think. Pictures would help.

Yellow labs often get black coloration on their bodies as they mature...it is called bearding on the jaw and can also be on the body. It is pigment and it is genetic. It gets darker when the fish is excited by breeding or eating, or when he is trying to disappear because another fish is more dominant. Clean yellow juveniles can develop it with age, so it is good to see the adult male parent when buying them if it bothers you.

Black brush algae is common as something you might be seeing on your rocks. What are your test results for ammonia, nitrite, nitrate and pH?
 

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Discussion Starter · #3 ·
Thank you for the information. My test results are 0 - ammonia, 0 - nitrite and 5 to 10 nitrate. Sometimes the nitrates get to 20. PH = 7.8 - 8.0. I'm posting two photos- One showing the black stuff on my rocks. The other shows the black on the yellow lab and another yellow lab without the darkness. I understand that some labs get the black coloration but these did not have. One of the labs that now have the darkness is about 1 year old. The other, is about 3. In fact one of the labs is #3 dominant fish. Also my Kenyi male (yellow) has it also. I will look into the Black brush algae.
 

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Discussion Starter · #4 ·
I should also mention that I seem to have the same issue in my 100 gal and 40 gal tanks. The fish, don't seem to be discolored in the 100g (Blue Dolphins) or in the 40 gal breeder (yellow lab and Hongi). The 40 gal doesn't get much, but it's noticeable when it comes and gets all over. It takes about two weeks, to form. I used Algaefix once per week and I have a phosphate remover in my canisters. My test for phosphate and silica are all within allowable limits.
 

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To me it sounds like algae...try reducing the light.

One of your labs has no black on the dorsal?

The labs look like what I expect if your strain has the black on the body...a comfortable fish ay be a cleaner yellow and an excited or sub-dom fish may show the black. It is situational.

The younger fish may be cleaner yellow...and the older fish may show the pigmentation.

Or it may be that as they mature there is more competition and more dark pigmentation.
 

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Discussion Starter · #6 ·
Thank you again for the reply. It could be algae. I will turn down the lights. I've struggled with different algae, green, brown and now maybe black. I use Algae-fix, change the water every 5 -7 days, and have phos guard in the filter. Some of my yellow labs show very little black on their dorsal while others from the same fry have it. All of my labs except 4, come from the same breeding group (1 male, 3 females). Both the dominant male and his son are the two labs that turned dark -at about the same time. The dominant male was purchased about 2-1/2 yrs ago. I have no idea on his line goes back to that dark trait. I also noticed that my Kenyi male (yellow) isn't as bright. In addition to reducing the light, I'm going to switch foods - just in case. Again thank you for your help and the information.
 

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I would not use algae fix.

Pure labs should have the black dorsal stripe for sure. If there is a fish other than a yellow lab back in their ancestry, it could explain why you are getting fry with different characteristics.
 

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Discussion Starter · #8 ·
That could certainly be as I have no idea what's in the generations of the Male and Female that spawned. So far, the ones that have come out without the black on the dorsal, usually get the black before they are adults. Lets hope this pattern continues - One strange thing, all of the ones that have come out without the black on the Dorsal, have been female. If you have an alternative to algae fix, I'm all ears. I've reduced silica, phosphate, fed less (spirulina). I have lights on 4 hours in the morn and 5 hours eve/night. Again, thank you for all of the information. It's truly appreciated.
 

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Cut the lights in half. Make sure there is no sun coming in from a window.
 

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Discussion Starter · #10 ·
Great, I will try this. I skipped feeding Omega one pellets for two days and did a 60% water change yesterday. Included cleaning rocks, and substrate. Amazingly the two yellow labs where the dark shade appeared most is almost gone. I can't believe this is residue from fish food and algae, but I'll certainly watch and report back. Thank you again.
 

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The black on the fish is pigment. If it went away you would interpret that to mean they are happier due to cleaner water. Their mood is turning on or off the pigment.

The black on the decor is algae. Cleaning the rocks removes it but if you have excess nutrients (nitrates and phosphates) and light then it will come back.
 

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Discussion Starter · #12 ·
I'll keep my eye open as the change in pigment on the fish is different for me and they are the only yellow fish that have changed. Prior to the water change the nitrates were about 10. After the change they are about 5 and phosphates are less than 0.5. I'll try feeding less and of course I switched foods, as I noticed the tank that I don't feed that particular food, but keep the lights on the same amount of time, does not have the black algae. Again, thank you. Very Helpful.
 
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