need help id'ing white gunk in gravel

[nyghtskye]

Hello, i would love any information anyone has to offer. Last week we noticed a small bunch of white 'gunk' in the gravel. It disappeared by the end of the day. Today we noticed two more spots. The fish seem fine and healthy, I'm just worried it might be the first sign of a much bigger problem. I'm attaching a picture of the spot that is along the edge of the tank. I would appreciate any information anyone might have and Thank you in advance. I just check the water, 0 ammonia, 10 nitrate, 0 nitrite, 6.4 ph, hardness about 225ppm.

We have an established (7 months) 29 gallon tank with: 6 glo tetras, 1 black phantom tetra, 2 female and 1 male guppy, 2 cory cats, 1 black ghost knife(it's still a baby, only 4 inches long), 1 chinese algae eater, 2 female 1 male and dozen baby velvet swords( they are 2 weeks old).
We started with undergravel filter and added a 20-40 gallon power filter. We only have artificial plants in the tank.

[Judge]

Not sure what that is from the pic. Welcome to FTF, I am sure someone will be along that might have a clue. You might be a little heavy on the bioload for a 29 gallon. What, if anything, in the way of chemicals have you added? Anything new just before this white stuff appeared?

[nyghtskye]

my husband isn't worried (fish seem fine) so we haven't added any chemicals. the most recent addition is the 2 cory cats. I had 2 albinos in my 10 gal and got 2 green for the 29 gal, my husband decided to put one of each in both tanks. the 10 gallon is fine. we added the power filter to the 29 gal about 3 wks ago. the 10 gal only has powerfilter.

[Judge]

I would watch it but as long as all your water params look good and the fish seem fine I would not worry.

[louistheloach]

it looks kinda similar to a post by someone else except they had it on the glass and it moved around the tank.....cant remember the name of the post or the poster....if I come across it I will let you know..........

ltl