I had some years ago 100L low tech with soil from garden and gravel. Sometimes changed water every 3 months sometimes 6 months, or simply can't rememebr any shedule and never thinking about exact shedule
Two fluoriscent bulbs, can't rememebr exact but good light over 1wpg, manualy switching on and of every day in different times.
A lot fastgrowing plants and fishes + hangon small filter with only floss media
No any ferts, only once i fit some root tabs in to gravel.
No heater, only room temp.
Plants growing well.
Never had any algea, except after non longer water changes got slightly green water.
This tank less maintenace i ever had.
About introducing co2 with water changes i'm not sure. I don't agree, sorry.
I think easily with non problems can change 20%, 30% or other amount of water weekly or monthly or longer periods or every day.
Water changes is good in any amount until Yours water is good and approx. same parameters.
Instead i before used airstones in low tech near some plants, plants get litle co2 and tank o2 from air.
In night time( i used air stones 24/7) injecting air is necessary for healthy low tech. And what's difference small introducing co2 with water changes or via airstone feed tank with co2, or via surface agitation or both combinations.
If tank have good areation - airstones, surface agitation Yours co2 going out imediately and in one time introduce gases from air in to tank like gas exchange process , that why i'm keeping 24/7 aeration and why i put small airstones near some plant roots-gravel, i believe plants can extract from air little co2
Or where is this TAP water with so high co2 concentration , can cause problems in tank ?
Best Regards,