new aquarium -- dandruff looking stuff -- what is it?

If you did not rinse the substrate extremely well, it could be just solid particles from the gravel. I'd try a finer floss or cartridge as Que mentioned. Or rent a Vortex Diatom filter and polish the water.
 
Hitman, I understand. I have considered getting a API Master Test Kit to use in situations like this (and until the tank is cycled), then going back to the strips for routine, 'no problems' daily testing. It's hard for me to justify the extra cost and effort when the LFS is getting the same results as my strips, though.

Featherfin, this stuff's about the same size, color and size of dandruff but I don't think it's actual flakes of dead skin -- at least I hope not! They are just tiny white particles, finer than sand. Maybe "snow" is a better visual analogy than "dandruff". Tiny, small, white dots. And they are not on the fish (like ich would be).

Que and rbishop, I will try using some different filtering media and if that doesn't work, look into renting a diatom filter. I tried scooping out some of this stuff using a net and a coffee filter. It didn't make the coffee filter feel gritty, but this stuff is so fine (finer than sand), it might not, even if it is gravel debris. I thought I did rinse the gravel well but I did not put it through a strainer, grrr. I hope I don't have to drain all 55 gallons out of the tank and start over to get rid of this stuff--I'm so close to being cycled.

Thanks for all your responses, they have been very helpful.
 
You shouldn't need to drain and fill again. Our LFS rents a vortex for $12 a day. The diatom earth will get it out for you, brobably in less than an hour.
 
ive found liquid to be cheaper since you get more tests, like 100-150 per bottle opposed to 20-50 that test strips give you.
 
Unless the particles are distressing your fish, I would NOT add Clarity or some other product to clear up cloudy water. It will make crap throught your canister hoses, and if you don't get it all out cleaning, your canister will "throw up" at some point, and you'll have a cloudy tank again plus gobs of biological matter floating around your tank.

Now that you're gagging, I can only say that I have the same problem at times. Good mechanical filtration is the answer, so you might want to look at renting a diatom filter, or perhaps trying a HOT Magnum (I've heard mixed reviews). My specks seem to float to the top, so I turn off the filter and bubbles before taking out cups of water to manage them.
 
Thanks, Shane. I don't like the idea of adding **anything** to the tank that isn't absolutely necessary. And actually, the water itself looks quite clear except for the tiny white particles suspended in it. What I mean is, it's not milky or cloudy like it was on the second or third day after I added the fish. And it's pretty much all through the tank, top to bottom. I can see it floating on the top of the water, if I'm looking up through the tank from the bottom; if I open the cover and look down, I can't see them. In fact, if I didn't have a black background on the back of the tank, I probably wouldn't see them at all.

Unless the particles are distressing your fish, I would NOT add Clarity or some other product to clear up cloudy water. It will make crap throught your canister hoses, and if you don't get it all out cleaning, your canister will "throw up" at some point, and you'll have a cloudy tank again plus gobs of biological matter floating around your tank.

Now that you're gagging, I can only say that I have the same problem at times. Good mechanical filtration is the answer, so you might want to look at renting a diatom filter, or perhaps trying a HOT Magnum (I've heard mixed reviews). My specks seem to float to the top, so I turn off the filter and bubbles before taking out cups of water to manage them.
 
OK, this morning I see that there is definitely a small but visible amount of brown algae growing on one of the fake plants and around the filter intake. Oddly, the amount of particulate matter in the water has decreased (I'm still looking for micron/'water polishing' media that will fit in a Penguin 350). I am going to look at this as a positive sign that this tank is nearing the end of the nitrogen cycle. The last water change I did was 6 days ago during which time the nitrites have remained steady at 0.5 (might have been closer to 0.25 this morning) and the nitrates are between 0 and 20. C'mon, Nitrobacter, multiply!
 
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