Help identifying problem

Update:

#2. The dark green areas on the leaves are algae. I was able to rub them off with my fingers.

This is my first real planted tank. It's a 20 gal high and only up for a little more than a week. I changed 50% water twice. I am starting to see some green algae on the substrate surface. I think I've overdosed since I have a nutrient rich substrate (mineralized soil and turface). So I am stopping the EI dosing and do another 50% water change today.

I am a bit puzzled here since the melting Jave Fern leaves pointing to lack of some kind of nutrient, yet algae is starting to bloom.

Should I lower the lighting a little?

I have the DIY CO2 at 1-2 bps feeding into the Fluval 104 filter. I don't think the CO2 is not dissolved properly because the Fluval would blows out a bunch of bubbles once in a while. Should I also add Excel to provide more CO2? I am looking into the Rex reactor.

All comments, opinions, or advises are appreciated. Thanks.

The java fern isn't melting, it's growing. New leaves are transparent on the tips.

I'm not quite sure what algae you've got there, kind of looks like cyanobacteria (blue-green algae), which shows nitrogen deficiency. Do some research to see if that looks right, and if so increase dosing of Potassium nitrate (as EI recommends), and perhaps decrease light until problems clear up. Verify that you are dosing correctly as EI recommends.

Also, I'm sure you know this, but java ferns should not have the rhizome buried in the substrate. The brown "roots" can be buried, but not the rhizome. I can't tell from the pictures if this is how you've planted it.

Do you have a test for ammonia? I'm guessing with your new setup, and with a soil based substrate, that there is probably some ammonia in the water column, which can spur algae blooms like what you're experiencing. Reducing light and keeping up with water changes will help here, as well as manual removal of algae.

Keeping the CO2 as high as possible is also important. 1-2 bubbles per second is a meaningless method of measuring the amount of CO2 in the water, bubbles per second is only useful in seeing if the rate at which you are introducing carbon to the system is increasing or decreasing (since bubbles can be small or large). You may want to try to increase CO2 production of your DIY system by adding another bottle of mixture. If you do this, make sure to increase O2 levels as well by increasing surface movement. High levels of O2 and CO2 will make for a happy and healthy tank. Good luck.