Black spots on leaves

[SSeelye410]

Hello all, I have a 20 long tank with 6 corycats, 6 neon tetras, 2 nerite snails and a golden mystery snail. All of my plants are live plants, and in the last couple weeks they have been developing black, rough feeling spots (pics included). The spots aren’t hairy like BBA and the plants are continuously growing and growing new leaves so they aren’t dying at all. My water parameters are good, I use the same water and plants in a different beta tank and there are no black spots on those plants. The only thing I can think of is the light is too bright and on for too long causing some type of algae buildup. (Aqueon LED optibright, on for 12-14 hours a day due to work schedule). Any idea what exactly it is and how to fix it?

 

[ZxC]

That is an algae growing on old plant leaves. This type of algae will only grow on unhealthy portions of a plant. Just because it is sending out new growth, does not mean it is entirely happy. Decaying plant material releases sugars / compounds / ammonia that are needed for algae spores to germinate.

I will need some more information on your setup.

What is the distance from the light to the substrate?
What fertilizers are you dosing?
What plants are in the tank?
What other compounds are you dosing?
How many / how large are your water changes?
How often are you cleaning out your filters?
Is there lots of ambient room light or direct sunlight hitting the tank?
What are your tank parameters? Too many people say their parameters are "good" but in reality they are misled. I'm not accusing you of being misled, but giving actual quantified values will be more helpful than saying they are "perfect".

pH
kH
gH
TDS
Nitrate
Nitrite
Ammonia
Phosphate
Anything else you can measure.

12-14 hours is too long, unless the light it very dim. 8-10 hours is plenty, even for a low light tank.

Manual removal is key. Remove all bad looking plant material, it will not recover.
Clean filters (in old tank water during a water change) every week or two.
Remove as much organic material as possible.
Get a good fertilizer routine setup. Healthy plants will inhibit algae growth.
Ensure your levels are within good parameters.
Start dosing a glutaraldehyde product such as Seachem Flourish Excel or Metricide 14.
Increase both the size and frequency of water changes.
Buy a clean up crew. Nerite snails, oto cats and amano shrimp are a good start.
Reduce lighting to 8 hours a day.
Reduce any sunlight that may be hitting the tank.

These are all a good starting point. If you can provide answers to the above questions I can help you out some more.

I hope this helps.

 

[SSeelye410]

I don't have all the answers for you, I'm new to this still, sorry! The tank has only been set up for about 2 months now. I do weekly water changes, normally 25% at a time. I rinse the filters every other water change. The cartridges were brand new when I started the initial cycling. No additional sunlight. I don't use fertilizer, picking up flourish/excel tonight. I have flourite gravel substrate which is supposed to have added nutrients in it. The tank is about 12 inches high and the light sits about 1 inch above that. Substrate is only about 1-2 inches thick. Plants include different types of ferns, swords and moneyworts. The moneyworts are older and came from a previous tank I had. I have only used the cheap Tetra easy strips for testing the water:
Nitrate: 15
Nitrite: 0
Hardness: 150 (hard)
Chlorine: 0
Alkalinity: 40 (low)
Ph: Neutral -alkaline
Ammonia: 0

I'm hoping with Flourish/excel, reducing the light to 8 hours a day and getting rid of the infected plants will be enough?

 

[ZxC]

I don't have all the answers for you, I'm new to this still, sorry! The tank has only been set up for about 2 months now. I do weekly water changes, normally 25% at a time. I rinse the filters every other water change. The cartridges were brand new when I started the initial cycling. No additional sunlight. I don't use fertilizer, picking up flourish/excel tonight. I have flourite gravel substrate which is supposed to have added nutrients in it. The tank is about 12 inches high and the light sits about 1 inch above that. Substrate is only about 1-2 inches thick. Plants include different types of ferns, swords and moneyworts. The moneyworts are older and came from a previous tank I had. I have only used the cheap Tetra easy strips for testing the water:
Nitrate: 15
Nitrite: 0
Hardness: 150 (hard)
Chlorine: 0
Alkalinity: 40 (low)
Ph: Neutral -alkaline
Ammonia: 0

I'm hoping with Flourish/excel, reducing the light to 8 hours a day and getting rid of the infected plants will be enough?

Flourish is good for micro nutrients only. It has very low amounts of PO4, NO3 and K.

Flourite has 0 nutrients in it and is completely inert. Instead of flourish, look for Thrive or Aquarium Co-op's all in one fertilizers.

Use Flourish Excel as per directed on the bottle, or up to 1.5x that rate.

Reduce lighting time (8-10 hours) and manual removal. That should be a decent start. Might want to try some root tabs for crypts / swords.