PlanetCatfish.com

Last night I discovered two colonies of slime mold in my 33g hex fish tank. One of them looked like a 2D cobweb spread over a few square inches of the glass where it meets the gravel. The other looked more like a 3D sea anemone no bigger than a cubic inch.

In a few hours time, both of them had moved. The cobweb one had transitioned from the glass to the gravel and was webbing it's way over & under & between the rocks. The anemone one had traveled downward on the glass and had differently shaped "tentacles" both on the glass and out into the water.

This morning the anemone was on the gravel and spreading down into the gravel. The cobweb one was not visible... though I didn't look too hard.

I'm not finding a ton of information on them on the internet. This page has great photos of what I saw. http://waynesword.palomar.edu/slime1.htm

Do you have any advice? In all my years of fish keeping I've never seen this before. And this tank is barely 2 months old. It has a piece of mopani wood (which went through that white fuzz phase), several live plants (horwort, vallisneria) a few tetras and a few clown plecos. The clown plecos were the newest addition about 1 month ago.

I didn't test the water recently, but about 2 weeks ago all nitrate, nitrate, and ammonia readings were at nearly 0ppm. pH around 7.4 and temp around 75degF.

I didn't think to take photos. If they're there later tonight, I will.

I don't necessarily want to kill them or remove them, but if they are harmful or if they are a sign that something is wrong with the water quality, then I want to rectify the problem. I have to admit they freaked me out, and it took me a while to guess that they were aquatic slime molds (I knew terrestrial ones existed... but not aquatic... so thanks internet for confirming my hypothesis. LOL).

Thanks!

I just took a photo. The anemone-like one is now completely on the gravel and changing into spider-web shape.

http://www.badbear.com/SlimeMold.jpg

Basically I'm trying to learn if this is bad? or nothing to worry about?

I made a couple of animations too. The first one is at 10 minute intervals. When I realized it was crawling up the glass, I re-setup my camera and took pics at 5 minute intervals but the darn thing crawled out of range of focus after 20 minutes. #outsmarted
http://www.badbear.com/SlimeMold1.gif
http://www.badbear.com/SlimeMold3.gif

I have seen this stuff appear in some of my tanks over the years although I never microscopically examined it to determine what is is exactly. I don't believe this is a true slime mold. My guess is that uneaten food is accumulating between the somewhat coarse grained substrate and that is sustaining the growth. You may try adding some Amano Shrimp to see if they don't eat bits of food and even the growth.
Otherwise I don't think this poses any immediate threats but should be taken as an indication that there is room for improvement with regard to tank hygiene.

Ooh, it does look like a slime mold, but it could also be any number of other weird microscopic beasts.

There is a slime mold group on Flickr. If you have a Flickr account, try posting it there -- best to post this kind of question where slime mold experts congregate.