Can you diagnose spots, frayed leaves/stems and slow growth

[jodacro]

This is a 20 gallon freshwater tank w/ six Tetras, Dwarf Gouramis, medium-sized Angel fish, three Kouli Loaches, five Siamese Algae-eater, and a few others. Floor of tank has red, iron-rich substrate, two large pieces of driftwood, rocks and a large clam shell. Each week I change out 20% of the water, treat new water with Seachem Prime and add in two capfuls of Yamato Green. The tank gets 12-13 hours of strong light and water temp is mid 70s.

About 4 months ago the tank developed a terrible case of Black Beard Algae and I can to severely trim out many of the plants. (That's when I got the Siamese Algae Eaters.) My local fish store recommended I remove the charcoal pack from AquaClear 50 filter and replace it with an additional pack of clay pellets.

Since the Black Beard Algae infestation the plants have not done well. See attached images. What can I do? What am I doing wrong? (Thank you.)

[DrNic]

If you added the clay into the system then you're probably absorbing the nutrients out of the water that the plants need. It's going to slow down the algae but also be detrimental to the plants as well.

First I would try removing the clay and see if the plants start doing ok again. (Keep in mind this might bring back the algae).

Assuming the plants start doing better when the clay is gone, I would then start a regime of hydrogen peroxide treatment, blackouts and reduce feedings to get rid of the algae.

The worst part is that beard algae will hang around (literally) even after it's dead so you may need to do a complete overhaul on the plants to remove any signs of it before you start so you can tell if there is any new growth or not.

[smaug]

You have all those fish in a 20?You will forever be plagued with algae problems with a bioload like that.I dont know what is up with your particular plant troubles ,but you gotta thin out the fish load.5 sae are far too many for a 20,they get 4-5 " each and need more territory then that.Sorry to be blunt but at the moment you dont have just algae trouble.

[MCHRKiller]

What exactly do you mean by strong lighting? What is your wattage? IMO as BBA is caused by excessive nutrients, ie decaying food...to high of a bioload...to much ferts. AI would remove all filtration material that is not biological or mechanical...you need nothing else in a planted tank. Also what plants do you have in there? To many slow growers and no fast growers will also lead to an algae problem IME, include atleast 1 quick growing infestation style aquatic weed into every tank and your algae problems will be cut in half as any excess nutrients will be sucked up by said plant.

Planted tanks are about balance between your stock, your ferts and your lighting. Your plants are suffering from nitrogen deficiencies as well as potassium and iron IMO from those pics...most likely due to being sucked out of the water by the clay as Nic suggested. I have also found that having 2 photo periods works better than 1 long one in controlling most types of algae(BBA however is not caused by lighting) to prevent future issues. I keep my tanks on a timer of usually around 4-5hrs on...2-3hrs off and 4-5hrs on again.