Black spots on my java fern: causes and solutions

[shellby]

I'm using Flourish Excel, it's the liquid version. My GH is 75, or at least that's what the little bottle says - it's labeled as soft.

[boomer]

I've got a Java fern with these weird black spots on the top of its leaves, and honestly, I'm stumped. Can anyone give me a clue what's causing this or how to stop it from happening?

The 75 ppm GH is perfectly fine, equating to 4 dGH, which should cover your plants' calcium and magnesium needs with the Flourish Comprehensive. I'd recommend increasing your water changes to once a week, though - this will help replenish those minerals.

Regarding the Excel, I'd advise against using it once you have fish in the tank. It contains glutaraldehyde, a potent disinfectant used to sterilize surgical instruments and even in embalming fluid. It's far too harsh for an aquarium, and while it won't kill your fish outright, it will weaken them. Some plants, like Vallisneria and certain mosses, are even more sensitive and can die from the recommended dose.

To be honest, you don't really need the Excel anyway. The organics breaking down in the substrate will provide enough CO2 for your plants.

[shellby]

I'd suggest stopping the iron additive for now. Given that you're using Seachem Flourish, it likely already contains sufficient iron for your planted tank. Excess iron can indeed cause problems, either directly or by hindering the plant's ability to absorb other essential nutrients. The black spots could be an indication of this.

As a shade plant, Java ferns are probably not too fussed about light, so that's unlikely to be the issue. However, I do wonder about your CO2 setup. Are you using a diffused CO2 system or something like Excel?

I think stopping the iron additive is a good idea. Flourish Comprehensive Supplement for the Planted Aquarium already has enough iron for your tank. Too much iron can cause problems, either directly or by stopping plants from absorbing other nutrients.

As a shade plant, light probably isn't the issue. But the CO2 might be. What kind of CO2 are you using, is it diffused CO2 or something like Excel?

[boomer]

I've been using Seachem's Excel as per the instructions and it says on their website that it's safe for fish, with ingredients listed as polycycloglutarcetal and water. I've stopped dosing iron and increased my water changes to once a week, but it's been seven weeks now and I'm not seeing any improvement. I've also noticed that the bottle of Flourish Comprehensive Supplement says that micronutrients can be purchased separately and aren't included - could this be the issue? Unless, of course, plants can get diseases too.

I've been thinking about what you said regarding Excel, and I'm not sure I agree. I do see your point about its potential impact on fish, but I've been using it as directed. I'm more concerned about the lack of micronutrients in the Flourish Comprehensive. I've been using it as recommended, but maybe I should look into supplementing with additional micronutrients.

I also noticed that I have some algae growing on the glass, which I suspect might be due to excess light or nutrients. I'll have to keep an eye on that and see if I can adjust my setup to prevent it.

[shellby]

I'm still stumped, if it's not the lighting, nutrients, or where it's placed, then what's causing these black spots?