Thank you, Highseq! I have to test my phosphate and nitrate levels when I get home.
The plants that the algae is growing are not doing too well. It is mainly growing on my medium/slow-growing plants-- a crypt wendtii and red nesaea. I am thinking of getting rid of the red nesaea because I read that it is very difficult to maintain. I also get green algae on the glass pretty quickly. I think it might be a hair algae and GDA combo! My swords and ferns do not have algae on them.
Until I get all my parameters checked, I am going to do a few things you recommended; I'll run one light instead of two and drop the photoperiod an hour.
General question: Is there a practical way to check for fert imbalances? I would love to dial in the amounts I need, but I am fairly new to Co2 and ferts. I am not sure what I should be testing for. I kind of just look at the plants to see how they are doing.
Firm believers of the EI method would tell you to throw away your test kits and just scale the dosing ratios to your tank. I find testing every parameter I can very helpful when starting out as it tells me how my levels fluctuate throughout the week and how much my plants consume a day. I will give you my opinion, but it is exactly that, my opinion. Others I'm sure have their own preferences.
I use the seachem iron kit and really try to keep my iron at a constant .2ppm, but really you can keep your iron levels at .5ppm and probably be fine. I then test my nitrate levels. I dose nitrate after a water change to 20ppm. I have a really high bio load in my tank and have figured out that after 1 week my nitrate levels will be around 30-32ppm, so I actually only dose nitrogen once a week. I have stopped dosing phosphate altogether because my fish actually produce enough without me adding any. by the end of the week i'm at around 4ppm which is higher then I would like to be honestly. If I really was having problems I could put a little phos-ban in my filter but I don't feel the need to. There is no really good way to measure potassium so I just dose it twice a week. Out of the macros it is my understanding it can be tolerated at the highest levels compared to the other ferts. I dose my micro mix 3 times a week.
Initially when I do my water change I make sure my kH is about 5, my gH always hovers around 12, and I add liquid calcium chloride until I get to 80ppm calcium (but this is just my preference for my snails).
Most people would say this is wayyyy overkill, and I don't disagree. But this is a hobby, and for me half the fun is tweaking things.