A Python water changer is the best time investment
(I’ve used alternate branded systems but quality, especially of the tubing, is no where near as good)
Just start syphon and drain to garden or toilet etc to save on water usuage (though Python does claim a 7:1 ratio once started (which is consistent with theory) - certainly the outflow water does run close to tank temp rather than the cold tap water, but that’s the extent of my measurement ... note if your tap pressure is low, it can struggle to start the syphon from tank (depending on distance and height) and will waste water during this stage)
Refill tank directly from tap, adding sufficient Prime for entire tank volume (depending on tap additives, you can omit Prime if no livestock - as I usually have a cycled filter, I add shrimp and snails the day after tank setup)
With the twice a week water change, I’d aim for 70%
Check each day for any melt and do a quick syphon to remove any debris (maybe 10% water change to do this)
Even 20% daily should increase CO2 levels in water - obviously one can also add sparkling water but most contain significant sodium levels, if you have a SodaStream system, just carbonate some tap water and add to tank
I find that melt becomes obvious around the second week - but this is going to vary with temp, also lighting and CO2
You might run 24/7 CO2 - usual (higher) rate during photoperiod, reduced rate during off hours - this should maintain a slightly elevated background CO2 level; this is more relevant if tank is in a bright room rather than a (very) dim corner
forgot this is non-CO2
If you plant R Vietnam H’ra, you can see the (surprisingly) low level of ambient light needed for leafs to “open”
(this plant grows rather nicely in non-CO2 and will show pink even in quite low light, slow growth setups, it’s become one of my favourite plants)