Those are two problems right there. Too much lighting, too much nutrients to feed algae.
Nitrites are toxic to fish and if you are able to read them with your API master test kit, your biological cycle is not complete. A healthy established tank should produce nothing but nitrates and the PPM of nitrates will creep up daily between your water changes. I don't allow nitrates to exceed 20ppm in my tanks. I tend to do weekly ~75% water changes. One of my tanks can go every 2 weeks. Excessive nitrates will eventually make the fish unable to fight off illness. Not changing enough water and just topping off will eventually skew the dissolved solids in the water column to the point the pH will crash and kill everything quickly. This is another reason why regular water changes are important. It will keep your tank's water parameters in line with your tap water.
I hate bio-wheel hang-on-back filters. AquaClear is a much better option with rinsable sponge media.
I may have gotten the nitrate/nitrites things mixed up. My test kit normally registers zero of the bad one and a few ppm of the less harmful one. That one usually registers in the safe range of ppm like you mentioned. It's not a lot of ppm.. maybe something like 20 as you mentioned. I have had the bad one spike on me before if say a fish dies and I don't notice it for a few days or the fish get overfed, sometimes my daughter will drop some food in to "play" with the fish. She likes how they come to the top and nibble on her finger and she can "pet" them.😂
Yeah, I'm not to fond of the non-replenishable (one and done) filter media, the cost adds up. I've thought about ditching it and seeing if I can get a large piece of that washable sponge media you're talking about and trim it to fit. Just never got around to it..
I think I'm gonna ditch the Tetra water maintenance stuff (are you familiar with it?) and go back to water changes. TBH, I started using it because I just got lazy about the water changes. Funny thing is I usually have clear water for the most part, so can it still be cycling? The only time it gets cloudy is when I overfeed.. it's a sign that I am and need to hold back on the feedings.
I've got a couple extra of those smart home plugs I use for living room lamps. They're connected to the Alexa ecosystem I have going. I can set them up on a timer basis so that will help control the light time. Do you guys think it's better to run an old fashioned tungsten lamp as opposed to a CFL??
I haven't really considered using a under gravel filter or the sponge filter that SirTannon suggested because I didn't want the sound of a pump. In the old days pumps were pretty loud but maybe they've gotten quieter.. anyone have a recommendation on a quiet air pump?
But as to treating/killing the algae it sounds like there's no direct stuff to do it... just kinda address what's causing it to grow (light, water quality etc)?
Here's a pic of the tank..I recently moved the plants most covered with the algae to the opposite side of the tank (to the left in the pic). If you look closely you can see the black brim on the plants, that's the algae.
Also, any ideas on why I have such a hard time maintaining pH around 7? Both of the alkalinity and pH like to drop off and the pH settles around 6.2'ish usually.. which isn't horrible for some of my fish like the Molly's (iirc prefer brackish water) Betta (I understand they prefer a slightly acidic water?) but the Cory's and Platty's I think prefer a more neutral pH. So I've been trying to keep it around 7 but no lower than say an upper 6. Wonder if the tap water i add to top off is acidic, never tested it??🤔
Anywho..I appreciate the advice. I've got a couple things I can change up.