I'll try, please bear in mind that english isn't my first language, it is my third and I'm still 'in progress' ...
I don't feed much in general, as my tap water already has a salt load of 1,5g/l. Therefore I must prepare different 'waters' for different plants. When I run out of rain water (June or July) I buy water with low salt content. This water I use first in my aquaria, and afterwards for my plants. As I cannot use tap water for flushing surplus of salts, I must prevent salts building up at any rate - until it rains.
Big and special plants get extra feeding. When I fertilize these special plants (professionals please stop reading now) I do it
ad libitum ... er,
freely, the liquid fertlizer I used these days is the cheapest, (5-5-5, 2,02% N - ammoniacal, 1,61% ureic, 1,43% nitric) and I pour a bit of it ....
into a 4 l vase and from there I water the plants ... and as long as there is water in the vase, two, three, four days ... so I can't tell you ppm's. Two or three time a month I add a bit of algae extract to this watering-water ... and sometimes epsom-salts; this roth is the only one that gets half a tea-spoon of epsom salts directly on the surface of the substrate, twice a year ... .
So this is not scientific, nor
is it horticulture, (I should know it better)...
Now is summer here, and humidity outside is very low, even if I spray four, five times a day, the substrate does not hold water very long, so I need to water every second or third day. In about a month this will change, and I will reduce watering to once a week. Accordingly there will be less fertilizing.
I can't tell if I feed every third or every fourth watering. It depends on the weather: during very hot and sunny spells I don't feed at all - I even try to use the cleanest water (least organic load), warm and cloudy weather encourages me to fertilize much more. Dry spells (air humidity less than 40%) - and I don't feed.
The pots are normal pots. Even if the saucer is completely full with water, there will be just a little water eventually touching the roots - not like semi-hydro, because of the (5 mm) rim the pots have to prevent them from sitting in water.
And yes, the black pot is to prevent algae.