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Looking to figure out what this is and how to get rid of it. Found it in my pleco tank. Thanks so much.

I have no idea. Looks like a fungus, but that's just a guess.

Cheers, Eric

It is a form of freshwater sponge, or so I am told; indicative of good water upkeep and whatnot, not really detrimental in any way.
I could be wrong, though; might be best to wait for others to chime in.

I will second freshwater sponge. Probably from the genus Ephydatia.

I have some as well, and the only problem I have is it's in a planted tank and it kills plants it covers, it spreads by spores if you move anything from an infected tank to another, and I have yet to discover a way to kill it other than manual removal (but spores remain and it comes back).

OregonOutdoorsChris wrote: 21 Jan 2025, 14:38 I will second freshwater sponge. Probably from the genus Ephydatia.

I have some as well, and the only problem I have is it's in a planted tank and it kills plants it covers, it spreads by spores if you move anything from an infected tank to another, and I have yet to discover a way to kill it other than manual removal (but spores remain and it comes back).

Do plecos seem to eat it at all? I know there are a good number of species (Parancistrus spp. for instance) that consume freshwater sponges; likely a completely different sort of sponge, but those white flat blob things are still sponges...
Odd that it seems so invasive. The few people I know that had them found that they were slow growers and typically only grew on rock, wood, or glass; perhaps some species are far less particular and sensitive than others.

I don't have any plecos, so I could only guess. If there were a commonly available pleco species that is easy to care for and eats this sponge, I would certainly be interested in hearing about it .

But from my experience so far, I can tell you otos, cherry shrimp, and amano shrimp don't eat it.

Fallen_Leaves16 wrote: 21 Jan 2025, 14:51

OregonOutdoorsChris wrote: 21 Jan 2025, 14:38 I will second freshwater sponge. Probably from the genus Ephydatia.

I have some as well, and the only problem I have is it's in a planted tank and it kills plants it covers, it spreads by spores if you move anything from an infected tank to another, and I have yet to discover a way to kill it other than manual removal (but spores remain and it comes back).

Do plecos seem to eat it at all? I know there are a good number of species (Parancistrus spp. for instance) that consume freshwater sponges; likely a completely different sort of sponge, but those white flat blob things are still sponges...
Odd that it seems so invasive. The few people I know that had them found that they were slow growers and typically only grew on rock, wood, or glass; perhaps some species are far less particular and sensitive than others.

Quite a few genera are reported to, I believe Megalancistrus as well, maybe Pseudacanthicus as while carnivores they do have some very robust teeth/jaws with more numerous teeth then normal for a carnivore. I'm not 100% they are digesting or actually eating the sponges opposed to extracting other organisms on and around the sponges. No doubt they probably wont feed on all sponges, there are images of those found in Loricariid habitats.
I believe quite a lot of the sponges want suspended sediment long term, there are also bryozoans which similarly filter feed and do occur in aquariums. This is also a sponge in my opinion, but no idea what sponge, there are so many freshwater sponge species.

I can now suggest Cupramine as a method for killing it. Though it's not 100% guaranteed.

Shortly after this thread was made I resolved to try to tackle the problem in my tanks. I removed all the fish and as many cherry shrimp as possible from the tanks to be treated, and I dosed the Cupramine as instructed on the bottle.

Within a week, the freshwater sponge was showing signs of dying off, the ramshorn snails were dead, the bladder snails were showing signs of distress, and cherry shrimp had some mortality but others in the population appearing fine.

Effects on plants was an interesting mix; vallisneria, dwarf water lettuce, and syngonium (emersed foliage) were all showing extreme distress, leaves wilting and dying. Other plants, misc. swords, crypts, anubias, sagittaria, pothos, and monstera all had no meaningful response to heavy doses of copper.

At the end of the two week course:
The sponge appeared to be good and dead with decay beginning.
The ramshorn snails were all dead.
The bladder snails now appeared to be copper tolerant and back to reproducing.
The cherry shrimp were reduced in count but appeared to be mostly fine.
Planaria popped up in one tank, presumably thriving on the death and carnage. So I redosed copper to see if that kills them, and it didn't ! So I had to resort to No Planaria, which worked as desired.
Copepods popped up in another tank. I did not desire their demise so I left that tank be .

About a month after:
All signs of sponge were gone, the vallisenaria and syngonium were sprouting new growth, and bladder snails were back to pest status.

Two months after:
2 of the 3 tanks are still sponge free, but I've been noticing something suspicious growing behind the plants in the 3rd tank for a couple of weeks now, and upon investigation discovered the sponge has returned.

So while Cupramine didn't finish the job after one go, I'm confident that a second round will do the trick.