Yeah! Oddly enough this happened to me, ad I don't know what causes it, but it seems to clear itself up after a while, so I wouldn't worry too much about it.

 

Yep, this sort of thing happens a lot. I think it's some sort of fungus that starts growing when the sap seeps out of the wood. It doesn't appear to be dangerous at all. You can just scrub it off. Boiling the piece of wood might also help.

 

Agree. I bought a nice branch of mopani wood last week, the first of this type I've ever had (been looking for over a year to find the exact shape) and although I washed it in hot water, two days later it was covered in white slimy fuzz and the tank water turned very cloudy. I took the wood out, gave it a real scrubbing with a stiff brush under boiling water, and placed it in a spare planted tank (no fish); in five days now it has not shown any more fuzz or whatever this is. And major water changes cleared the other tank.

I would also mention that the fish did show signs of stress--esp the corydoras, increased respiration-- hence the two major water changes; they are back to normal now and that was five days ago.

 

I have mopani wood in my tank and have had no issues with it.I plan on getting another piece when I find one I like so I'll be sure to watch for this slime.

 

I recently posted about my own slime-on-wood problem (http://www.tropicalfishkeeping.com/freshwater-aquariums/argh-can-you-identify-whats-growing-39458/) Is that what yours looks like, too? I never figured out what causes it, or a good way to get rid of it, but after a while I just gave up and found that it's starting to get better on its own. My fish didn't seem bothered at all, as far as I could tell.

 

I recently posted about my own slime-on-wood problem (http://www.tropicalfishkeeping.com/freshwater-aquariums/argh-can-you-identify-whats-growing-39458/) Is that what yours looks like, too? I never figured out what causes it, or a good way to get rid of it, but after a while I just gave up and found that it's starting to get better on its own. My fish didn't seem bothered at all, as far as I could tell.

I thought there had been a thread on this issue, thanks for mentioning it. In checking those photos, that is exactly what I had last week. From the accounts, it seems most prevalent with that mopani wood.

As I mentioned, in my case it also severely clouded the water; I had initially assumed tannins, but it was pure white and very cloudy, and removing the wood plus two successive water changes cleared it. The cloudy water did seem to bother the fish, the Corydoras especially, with laboured breathing which stopped with the water changes and has not returned.

I am leaving the wood in the fishless 33g for a while; I noticed this morning some slight white stuff on it, will scrub it again and keep it under water for a spell.

 

I am led to understand that it is a Saprolegnia sp. fungus growing on the wood. It will probably be best NOT to scrub the wood, as the fungus will disappear once it is replaced by a bacterial/algal biofilm, and this is what you are aiming for. The fungus is just the quickest organism to colonise it. One just needs to be a bit patient to let the bacteria/algae displace the fungus. If you keep on actually scrubbing it you will be removing any desirable bacteria/algae too.
I suspect that, as iamntbatman mentioned, the fungus is attracted there by sap leaching out of the wood. The piece that I had problems with very obviously had this fungus at all the cut ends of the wood, and not on the "outer" surface where there had been bark.
I have never had it so bad as it actually clouded the water (I agree, heavy water changes would be needed then). I have only seen it on one piece of wood, which lasted about 5-7 days until it disappeared. I just removed the worse of it with a syphon tube.
I did notice that my bristlenose and oto's definately did NOT like to at it. It clearly tasted revolting to them ! If it gets as bad as to cloud the water, I'm guessing that it could be very unpleasant for the fish.

 

That's interesting...I have had this happen in my newly set up tank that currently only has plants and snails. The wood is not mopani, but manzanita branches. I wonder if this fungus could infect the snails in the tank, which could then house the fungus and infect future fish stock.

 

Yes, that's what mine looked like. I've since rinsed it about 25 times in hot water and boiled it for about 30 minutes and after a final rinse, placed it back in my tank. The problem with the slime seems to have been taken care of as I see no evidence of it now. Thanks so much for your reply to my thread I learned from your experiences.

 

Thought I should share this with you, on this topic. I was in one of my local fish stores earlier today, and I happened to overhear a question from another customer. He had bought a piece of manzania [spelling?] wood (which I think is mopani wood under another name, it looks the same to me) last week, saw this fungus develop, cloudy water, and two of his three Corydoras keeled over and died within a couple days; the third is still "sitting" on the bottom. I mentioned to him of my experience last week that I've already recounted in this thread, and suggested he pull the wood out and do a major water change to save the cory. He said he had already done this, fearing something on the wood.

This is too much of a coincidence. It only serves to remind all of us that wood, even purchased from reputable stores, can have substances and vigilance is needed. Proper soaking, boiling, scrubbing, or whatever may be the best for the particular wood is a sensible precaution.

Another personal experience: back around 1997 I had a situation where fish were slowly but daily dying in my 115g, and I spent weeks testing and trying to figure out what was doing it; the corys again were the first to develop symptoms--laboured respiration, lethargy for days, then rolling over dead. Finally with the help of the Curator of Freshwater Fish at the Vancouver Aquarium I found the origin of the problem to be a large piece of wood that had leeched something toxic (still don't know what it was). Removing all the wood, scrubbing the tank, replacing the filter, cleaning the gravel, washing the plants--had to remove every trace of it, as it obviously had permeated everything slowly over time. That was also a piece of wood from an aquarium store. We don't know where this stuff comes from, or what may have sometimes been in contact with it, or what species of wood it may be. Caution is prudent.

Byron.