2 year old co2 injected tank, poor growth and algae
Hello everybody. I'm new to this site, just joined today. I have a 75 gallon that ive had for 2 years now. I've been in this hobby for about seven years now but started with plants two years ago. ive had a lot of frustration lately and have been getting very poor growth on all plants and lots of algae. Although I solved my bba and green spot algae by adding k2so4, ph2po4, and kno3 in powered form. I still have brown spot algae and the growth sucks on just about every plant. I've even tried a full RO setup and that only made things more problematic due to lack of minerals and ions. This is what I have
plants: anubias nana, anubias hostifolia, crypts, ludwigium, amazon sword, el nino fern, corymbosa, java fern, tiger lotus, and something else i don't or can't specify.
fish: 5 large angels, 3 small rainbow fish
lighting: i finnex ray 2 ds, two seperate finnex fugerays
equipment: sunsun 704 with uv, packed to the max with ceramic rings, no carbon, sunsun gyre wave maker to simulate a gyre, 300 watt fluval heater, 20 pound airgas cylinder combined with a co2 mechnical regulator that feeds the output spray bar, air pump that runs at night, glass drop checker
substrate, medium river rocks on top of seachem flourite, 3 inches of flourite gravel(clay based)
weekly 50% changes, then after water change I add a teaspoon of alkaline buffer to raise dkh to 5-6, co2 set at about 7bps which keeps ph at 6.6, drop checker always green, even at night, iron tablets added under the swords once a month, finnex ray 2 ds runs from 7am to 2pm, then air pump turns on and co2 turns off at 3pm. also after water change I add a capful of seachem flourish, capful of seachem iron(liquid), then 1/2 tsp kh2po4, 1/2 tsp k2s04, and 3/4 tsp kno3. I do this 3 times a week same with the flourish fertilizer and iron. So basically I'm dosing based on EL instruction for a 75 gallon.
GH always at about 120-180, dkh always at 4-6, ph always at 6.6 and hardly ever goes above 7, phosphates at 1-2 ppm, and nitrates usually in between 15-40. i havent had ammonia in over a year.
No matter what I do, change the lighting, turn on all 3 fixtures for super high light, or just run the ray 2 ds, no matter how much I raise the co2, or add more phosphates or fertilizer, i keep getting the same end result for the past year. And that is, poor growth and little bit of brown algae. People tell me to raise the co2, but from my understanding, the only way you can get 30ppm of co2 is if the co2 remains at 6.6 and the kh at 4 degrees. That is based off a chart I have. higher ph results in more oxygen and less co2 available per cubic volume of water, and lower ph results in higher co2, lower 02 and all that is provided the kh remains at 4 degrees. I don't know what I'm doing wrong her folks, been scratching my head for over a year, been to different people, aquarium stores and experts, forums. One guy says you have high phosphates. But then the next guy will tell me that no phosphates means plants wont fix carbon from co2, which means they wont use the fertilizer to sythesize amino acids and no growth. That leads to excess fertlizer and nutrients for the algae to consume. One thing is for certain, algae love to pick on the poor growing plants. Over the years I've also came across that about 50% of the people in the aquarium world are certain that phosphates cause algae and the other half says there is no scientific evidence that phosphates cause algae(in a co2 planted setup). amonia, co2 fluctuations, and improper ratio of phos to nitrates are the main reason for algae, in my best guess, or simply not enough of them. Last week, I upped the phosphates to 10ppm, and ironically, the algae stopped. Now I'm back to 1-2 ppm, and I have more brown algae and bba. In my discus tank, a tiny trace of phosphates leads to algae and I have to bleach the rocks, but in a planted tank, its a whole different story. My friend doesn't do anything with his tank, no co2, crappy flourecent lighting, and he doesn't understand any of the science, yet he's got beautiful amazon swords growing out of his tank. My swords reach a height of 4 inches, then just stop and start collecting algae, uuhhhhh!
I'd love to hear someones opinion. I've tried so many things and changed so many variables, am I missing a key nutrition? calcium maybe?