White Stuff Growing in Tank

Question
I have a 10 gal freshawater with black tetras, Buenos Aires, and neons. Over the last 2-3 months, I have noticed white stuff (looks like stretched out cotton balls) growing on the rocks and fake plants. The fish don't seem to be bothered. It grows from a few strands to whole blooms in weeks. I've cleaned the tank-vacuum rocks, cleaned the plants, water changes, replaced the filter-but it keeps coming back.

Answer
Hi Erika
Sounds strange.....But, it sounds like some kind of mold.  How often are you regularly cleaning the tank out?  If you're not doing this, you should be doing weekly water changes/gravel vacuums, changing out at least 25% each week.  The vacuuming is important to remove uneaten food and waste, because that uneaten food will grow mold on it-similar to "people food mold".  Also not sure how much you're feeding, but only feed once a day, what the fish will eat in a few minutes.  Net out any uneaten food.

Another possibility is some kind of fungus, maybe from the rocks.  I've heard of fungus growing on pieces of driftwood people find and add to their tanks.  Can't recall ever hearing the same about rocks though.  

If you're not doing weekly cleanings/gravel vacs, then start doing that and see if it helps.  If not, try removing the rocks and see if that works.  Maybe try boiling them as well, and you could try adding them back in.

One last thing I'm starting to think of now, I don't how many of each fish you have, but a 10 gallon is a bit small for the larger tetra varieties.  What are your ammonia, nitrite, and nitrate readings?  And are you using any kind of bacteria in a bottle stuff on a regular basis?  I ask, because years ago, one of my first tanks I set up, I did a fishless cycle on it with pure ammonia.  I didn't do any water changes on it, so the bacteria could grow.  I recall seeing a bunch of white stringy stuff growing in there as well.  I can't say for sure if that was part of the bacteria process, or if it was just mold though.  But, if you're water quality is off, or if you're using one of those bacteria in a bottle things(cycle, stress zyme, etc.) that may be the cause as well.

Good luck and let me know if you still have problems.

Christy