SMALL BUDGET GOLDFISH AQUARIUM 15 months update ..... STILL ALIVE AND HEALTHY

So it's been another 3 months since I tried upgrading my budget Goldfish aquarium and I broke the bigger tank .... since I put the fish back into their original 36"x12"x15" tank I haven't been using any artificial lights just natural light first time I've cleaned the front glass in those 3 months no algae growth at all with just natural light just a thin layer of whitish bio film.on the glass I been water changing 30% every 2 weeks since I upgraded the filters the fish are now around 7" so I don't mind if they stunt abit at this stage even though they shouldnt with water changing 30% every 14 days instead of weekly .... I'll see how it goes .... still looking for a reasonable priced 50 gallon tank if I find one I will upgrade them into it .... but for now they are still happy and healthy after 15 months in their budget aquarium.....