Help - Mold in aquarium


Help!!! I have mold growing over my gravel; I have a 30 gallon, community tank that gets a partial water change--around 30% once a week. I have a bubble rod, heater, and 3 stage filter along with led lights on the hood. I have a clean up crew of I standard Pleco, 2 cory cats, and three yoyo loaches. Also 2 neon tetras, 2 Danios, 2 black skirted tetas, 2 Congo Tetras, 4 diamond tetras, 5 Platys.Most of my plants are plastic. I have pink and black gravel on the bottom, and a stump with plenty of holes in it, a dinosaur ornament that fish can hide in , and a white rock with holes that the loaches love. The fish seem healthy, and I just found the patch of mold today.Where did it come from? Is it deadly? How do I get rid of it. I also had a red betta in my tank and had o remove it because it became mean to the other fish in the tank and bit some to death. He is in a separate bowl in the kitchen now. Can I put him back into the community tank at a later time and expect him to be a good neighbor? Thanks for any help.


When you say mold, I wonder if you mean like a white filmy goo that kinda surrounds one specific area and doesn't spread far out... Could be a bacterial bloom.

I just went through a google search and found, of course, an ...

I hope that helps...If that's it, some species like loaches, shrimp, etc will eat it right up and thank you later...Otherwise I dunno if it's bad for your tank if it's not that...


Welcome to FL!

Can you get a picture of it? What color is it? Could be algae....
How long has your tank been cycled and what methods did you use? ( fishless, fish-in, etc )
Do you know what your water parameters are?

Also regarding your betta - betta's are not social fish and prefer to be alone. They don't always do to well with other tank mates. An being that he has already killed some of your fish, its very unlikely he can ever go back in to that same tank again. Sometimes they do okay with other fish but in most cases, things turn bad and rather quickly. Its good that you separated him.


HI snofish welcome to FishLore!!

Is it possible it is leftover food?
It can become moldy if not eaten or vacuumed up.

If the betta has already shown such aggression that he killed other fish, imo, he should be kept in a tank by himself.




Thank you--it is a grayish film over the gravel. Not the whole tank, just a patch in the middle. I took out all of the plants and decorations and put them in a mild bleach solution to soak. I will scrub them tomorrow in warm water rinse very well and let them dry in our hot summer sun. I did a partial water change tonight, and vacuumed the gravel very well. It was very dirty--I could see brine shrimp that had not been eaten floating around in the murky water. I will work on more cleaning tomorrow, and then change my disposable filter.:;


I have had my tank for about 6 months. I have added fish to it a little at a time. I started with the Betta and for a long rime he got along with the other fish very well. Then he killed a Dalmation Molly that my daughter gave to me. It had beautiful fins, and I think that is what got the Betta angry. Next he got one of my diamond tetras. Then he went after one of my platys. I caught him biting my little Cory Catfish. He seems happy, blowing bubbles in his little pond on top of the microwave.


Thank you for your help. I vacuumed very well , and it seems to have gone. I am feeding less. The Betta is now in his own 10 gallon tank in the kitchen.. He used to be a good community fish, and suddenly became aggressive. It is a shame because he is just beautiful. snofish

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