You were trying to straddle the line between low and high tech, which is where you ran into issues. Did you have strong filtration as well?
The Walstad style low tech tank can have strong-ish lighting, but you would normally have light filtration and little or no fertilization other than feeding the fish. In a nutshell;
Start with some ferts/iron in the substrate to give the rooted, vascular plants a head start on the algae
Have some faster growing plants and/or floating plants to take up the nutrients, and rely less on nitrification/heavy biological filtration. The plants will take up the nutrients before they convert to nitrate if not competing with a filter
The nutrients limiting the growth will not cause the plants to die and you don't need to do a balancing act. The plants just grow more slowly without the EI ferts, CO2 and super high light driving them. This creates a win/win of less maintenance and pruning. These tanks thrive on neglect once you get them going.
This also creates pristine water and a really healthy environment for fish. I've had Neon Tetras live over six years like this. Then I started losing track of the original group members because they would breed and self replicate with no intervention. I had other fish that don't normally successfully breed and survive the fry stage in the main tank do so. Dwarf Gouramis, other tetras, corydoras, etc.
I actually had to stop putting more prolific fish like Kribensis into these tanks or I would have 100's in a few months...
Yeah, I think the lights were the issue that slide me into the high tech side. Not sure how to rate filtering, but I had a canister filter.
And then when the plants grew they would strip the water of some nutrients. Coming from the reef side prior, it was really eye opening that the biggest trigger for algae was the lack of balance in the nutrients. Because in the reef hobby, at least 10+ years ago when I first started, it was always get rid of nitrates and phosphates. But in my freshwater tank, I would purposely put both in and that would give me plant growth, but not algae growth. The nutrients would get unbalanced and then it was like the plants stopped growing and then the algae would come.
Also noticed what seemed like a decent relationship between Co2 levels and algae growth. Higher Co2 levels usually kept algae away. However, it's hard to say if it was a real relationship, as by that time I was already doing the EI method. The EI method was awesome. So much red in my plants, and they were lush. But after awhile it's just like ugh, I swear I just trimmed those plants.
I failed multiple times with the plants(lucky they are rather cheap) before going high tech.
So my hats off to those of you who get the low tech versions working well. In the end, I just figured I liked reef tanks better. These days I just have a 3g paludarium. I use the same type of plants in it, but only foreground and midground plants. Just put treated tap water in it. Very humid tank, glass top on. I use an air pump to pump fresh air in and blow on the front glass. No filter at all, just has a pump that powers 2 waterfalls/streams. Plants grew in fast(from seed some of them), but they are soooo much slower than high tech. No algae, but also no critters in, other than like nematodes in the soil. Turning my 25g cube into another paludarium after I put those fish in coral into the 180g.
Here's a short video from about a month ago on the 3g. It was shortly after I added the alternanthera reineckii(the red plants for those who don't know the names). It's grown in quite a bit more. I didn't think I would like the water area being heavily planted, but it's near full and I'm loving it. I just accidentally dropped the baby dwarf tear seeds in it. Should probably update a video soon, looks even better now.
