10 Gallon Tank Strange Patches on Java Fern

• Size: 10 gallons
• Age: 5 1/2 weeks
• Filter: Aqueon 10 QuietFlow with filter bag containing Marineland activated carbon and Zeolite blend to take tannin out of the water
• Ammonia 0
• Nitrite 0
• Nitrates 5ppm
• pH ≈7.2
• Stocking: 7 neon tetra, 4 zebra danio, 3 corydoras schwartz
• Plants: java moss, java fern, dwarf hair grass (just started)
• 1 large piece of driftwood, but I’m unsure what kind
• No fertilizers and no additional CO2 are being added
• Weekly water changes of 30-40%
• Substrate has added nutrients for planted tanks, but I don’t remember the brand

I have one large java fern that has been steadily making more little ferns for me to grow; the parent fern has been in the tank for just over 5 weeks. Over the last week and a half, I’ve noticed large, dark brown, almost black patches growing on one of the leaves. It's only on the top of the one leaf, not the bottom. I'm pretty sure it's not leaf rot or java melt, and probably not new ferns popping off. As near as I can tell, it isn’t harming any of the plants or the fish, and it hasn’t had any impact on the water quality. Does anyone know what it is? I’ve tried googling for it, but everything that comes up just talks about new ferns or java melt, and the pictures don’t match even slightly to what I have going. Is it bad and therefore something that should be trimmed out? I only have a few large leaves, so I’m hesitant to take one away if there's no issue.

Thank you for any help/advice!

Here are two pictures of the same leaf, front and back:

 

If you aren’t dosing ferts it could be melting/dying from lack or nutrients.

 

If you aren’t dosing ferts it could be melting/dying from lack or nutrients.

But wouldn’t melt show through the leaf? I’ve seen pictures of melt, and I’m pretty sure this isn’t it. Also, would it still propagate new plants if it didn’t have nutrients? It just dropped a new one yesterday.

 

H

But wouldn’t melt show through the leaf? I’ve seen pictures of melt, and I’m pretty sure this isn’t it. Also, would it still propagate new plants if it didn’t have nutrients? It just dropped a new one yesterday.

Hmm I guess maybe I’m wrong. That’s the only thing I could think of but that would make sense that it could be something else because it’s growing plantlets... I’m not sure what it could be. If they are older leaves doing that then maybe they are dying from being older?

 

H

Hmm I guess maybe I’m wrong. That’s the only thing I could think of but that would make sense that it could be something else because it’s growing plantlets... I’m not sure what it could be. If they are older leaves doing that then maybe they are dying from being older?

That’s possible. I have no idea how old the plant itself is since I bought it full grown. Or maybe it's getting too much light? It’s just a weak LED strip built into the lid, but it runs for 9-10 hours a day.

Also, I forgot to add that my substrate had a lot of nutrients added to it specifically for planted aquariums and to jump start the nitrogen cycle. I added it to the list of information.

 

That’s possible. I have no idea how old the plant itself is since I bought it full grown. Or maybe it's getting too much light? It’s just a weak LED strip built into the lid, but it runs for 9-10 hours a day.

Also, I forgot to add that my substrate had a lot of nutrients added to it specifically for planted aquariums and to jump start the nitrogen cycle. I added it to the list of information.

java ferns take in nutrients through the water/their leaves, not through the substrate/roots

 

Java fern throwing plantlets is actually a sign it's in distress, not a good sign. If it was in nature they'd pop off in the current and flow downstream to hopefully land in better water. Healthy java fern grows new leaves along the rhizome.

I'd take out the carbon. It's likely absorbing a lot of the nutrients before the plant can use them.

 

You don’t have the rhizome buried do you? It needs to be in the water column or it will melt. It’s either the plant dying or a type of algae outcompeting it and killing it. New plantlets mean it’s in stress and feels the need to reproduce before it dies off completely.

 

You don’t have the rhizome buried do you? It needs to be in the water column or it will melt. It’s either the plant dying or a type of algae outcompeting it and killing it. New plantlets mean it’s in stress and feels the need to reproduce before it dies off completely.

I didn't even think to ask that. Very important question!

 

You don’t have the rhizome buried do you? It needs to be in the water column or it will melt. It’s either the plant dying or a type of algae outcompeting it and killing it. New plantlets mean it’s in stress and feels the need to reproduce before it dies off completely.

I thought it was normal for them to grow plantlets off it’s leaves? Is it not?

 

I thought it was normal for them to grow plantlets off it’s leaves? Is it not?

It is! But it’s only been in the tank 5 weeks and it’s shoving out plantlets already along with this black death issue, which all points to suffering some sort of stress. A healthy big one can put out babies (mine hasn’t yet, sadly) but at a lower rate and usually not if it’s got any issues like this black that you are seeing, unless it thinks it’s a goner and about to die.

 

It is! But it’s only been in the tank 5 weeks and it’s shoving out plantlets already along with this black death issue, which all points to suffering some sort of stress. A healthy big one can put out babies (mine hasn’t yet, sadly) but at a lower rate and usually not if it’s got any issues like this black that you are seeing, unless it thinks it’s a goner and about to die.

Ohh ok. I was also thinking the OPs plant was maybe in some sort of distress and starting to die

 

I didn't even think to ask that. Very important question!

No, I’ve been very careful to leave the rhizome mostly free. There's only enough buried to keep it anchored in place.

Java fern throwing plantlets is actually a sign it's in distress, not a good sign. If it was in nature they'd pop off in the current and flow downstream to hopefully land in better water. Healthy java fern grows new leaves along the rhizome.

I'd take out the carbon. It's likely absorbing a lot of the nutrients before the plant can use them.

You mean the activated carbon in the filter? I only just added that a couple days ago, and this has been going on for over a week, so I don’t think that’s it. Also, if I take it out my water goes back to being brown from the driftwood.

 

You don’t have the rhizome buried do you? It needs to be in the water column or it will melt. It’s either the plant dying or a type of algae outcompeting it and killing it. New plantlets mean it’s in stress and feels the need to reproduce before it dies off completely.

The rhizome is not buried, only anchored to the substrate. As near as I can tell, this stuff isn’t harming the plant at all, but I’m a newbie to any kinda of aquaculture so I can’t be sure. If it is algae, how should I get rid of it, and wouldn’t it also show up on the other leaves of the fern/other places in the tank?

 

The rhizome is not buried, only anchored to the substrate. As near as I can tell, this stuff isn’t harming the plant at all, but I’m a newbie to any kinda of aquaculture so I can’t be sure. If it is algae, how should I get rid of it, and wouldn’t it also show up on the other leaves of the fern/other places in the tank?

Lots of algae has specific areas it prefers. For example, a lot of tanks will get a nice green coating on the bottom level of the glass and not anywhere else on the glass. In the same way, a lot of algae grows on plants because it is out-competing that plant and taking all it’s nutrients. Can you separate the black from the plant itself? If you can get it off, it’s likely algae. Algae is solved using algae-eaters like snails or by correcting the nutrient imbalance in the tank. This can take a lot of time. You need to figure out if it’s too much or too little light, too much or too little fertilizer, etc. First off I would start by removing the rhizome from the substrate completely and attaching it instead to the driftwood. Then I would probably decrease the length of time the light is on, because java fern are low-nutrient plants and typically handle less light better than too much light. What ferts are you using, if any?

I do not believe carbon would mess with the balance in the tank or cause this issue.

 

Even a little of the rhizome buried is too much. Anchor it to a rock or driftwood or other hardscape with super glue or fishing line. You can even free float it. But you should never bury any of the rhizome.

 

Lots of algae has specific areas it prefers. For example, a lot of tanks will get a nice green coating on the bottom level of the glass and not anywhere else on the glass. In the same way, a lot of algae grows on plants because it is out-competing that plant and taking all it’s nutrients. Can you separate the black from the plant itself? If you can get it off, it’s likely algae. Algae is solved using algae-eaters like snails or by correcting the nutrient imbalance in the tank. This can take a lot of time. You need to figure out if it’s too much or too little light, too much or too little fertilizer, etc. First off I would start by removing the rhizome from the substrate completely and attaching it instead to the driftwood. Then I would probably decrease the length of time the light is on, because java fern are low-nutrient plants and typically handle less light better than too much light. What ferts are you using, if any?

I do not believe carbon would mess with the balance in the tank or cause this issue.

So I went to pull any rhizome out from the substrate, but all that was holding it down were a few of those tendril things the fern grows that have snaked pretty far into the substrate; none of the rhizome was below the gravel. It probably got unburied during one of the water changes, but I don’t know which one it might have been or how long ago it happened. Either way, the rhizome is free. I can't really anchor it to the drift wood because of how the wood is shaped.

I just used the toothbrush I’ve been using to free loose food from the java moss to gently scrape the stuff on the leaf. The gunk comes off pretty easily, but it almost looks like a thin layer of leaf floating free rather than any kind of algae I’ve ever seen before, and I’ve never heard of a layer of leaf coming off a plant outside of those old biology class microscope lessons. I scooped the loose bits from my tank using my fish net. The java leaf below the dark stuff is a healthy green and look undamaged and none of the other large leaves are showing any sign of the stuff. I’m baffled. If it weren’t for this dark stuff I’d say the plant is perfectly healthy and normal.

I haven’t been using any fertilizers or dosing CO2. I was told that java fern and java moss don’t really need it unless you're trying to grow them more quickly, which I’m not really concerned about. I may start adding fertilizer for the dwarf grass I’m trying to rescue from my mom's beta's tank, but that's a different issue altogether and I want to see how that does with just the substrate first.

Here are a couple of pictures of the rhizome and one of the drift wood. It's kind of hard to get a good shot of the rhizome because it's angled towards me and the cory's hiding rock is in the way from the front.

Also, the last picture is of the newest fern. I haven’t separated it out from the parent, yet. It kind of looks like it's growing off the tendril stuff, not the leaf. Is that normal? That's how the last one formed too. I’ve never seen the brown spots on the underside of the leaves people describe.

Oh! And thank you for your help and advice!

 

Uhhhh the plant looks healthy to me. The rhizome is a nice green and it has nice green leaves and good roots. I’d say the stuff you are scraping off is just algae. Scrape it off each water change as needed and I think you’re good to go?

 

Uhhhh the plant looks healthy to me. The rhizome is a nice green and it has nice green leaves and good roots. I’d say the stuff you are scraping off is just algae. Scrape it off each water change as needed and I think you’re good to go?

Will do! I haven’t really cleaned it before so I’ll start doing that. If that doesn’t work, I’ll be back here again. Thank you again!