Here is how I count the tank full rule.
1" per gallon= good, no extra filtration needed.
up to 1-1/2" per gallon= need extra filter and at least 30% water change each week, or more as needed. test water at least every 3 days.
NEVER GO ABOVE 1-1/2" per gallon. (my personal rule)
Now here is how I count my fish.
Don't measure the tail, only the main body. Most fish count as 1" per 1" ,long skinny fish like khuli loaches count as 1/2 the measurement. dirty fish like most catfish including plecos count as double the measurement. extra fat fish add a little bit to the measurement.