High Doc Or Nitrates, Which Is More Dangerous?! Options

[Donny041280]

Hi guys,
my stats are:
1) 5 ranchu and 1 oranda
2) 360 liter aquarium
3) 6 sponge filter
4) cycled tanks NH4=0, NO2=0, NO3=depends..
5) feeding regime, 4 times hikari
lionhead with outofeeder, 3 or 4 FBW intervals 2 hours manually
6) wc 100% every wed and sunday
-If using well water everyday get supplement 30% wc(if i'm not lazy gets ,twice morning and night)
- using tap only wed n sunday 100% wc

explanation
I have and use well water with Nitrate 40 PPM for bout a year and its okay, fish healthy, but sometimes 2 fush have a white lump on head and bout week ago 1 of my ranchu has a hole in the head, i dont treat it just using liquid vitamins and soak it with my fbw and twice WC 30% everyday and 100% in 3 days, the disease is gone.. And hole got covered again with fat

Previously my tap water is not good the NH4, NO2 n NO3 is 0 but the water is like yellow mud even after i filter it.. but recently the water is clearer than my well water so i'm started to use tap for my aquarium
And it's good that the fish get zero nitrate in.. Err bout 1 day only? (due to my heavy feeding)

Questions
1.which is better?using well water or tap?
Pros and cons
Well water
+
1.could change more
2.low bad bacteria, DOC and pheromones
3.cheap ( i could change 500 liter a day and the next day my well get full again)
4. No cost in water conditioner
-
1.very2 tiring
2.they never get zero nitrates

TAP
+
1.zero nitrate
2.on WC 100% days i could disinfect my tanks with chlorine as i take all the fish and sponge and pour the water till full then put anti chlorine
-
1.could only change 100% twice a week due cost on water and water conditioner

Well guyz, which is better?
apples or oranges?!?

Thx,
Donny