Do indeed need number's with respect to the water you have from the tap after it has set overnight.
While GH and Kh would be helpful,, A pH reading would give a fair idea as to what type of water you have.
It is possible to cycle the 75 gal while still enjoying fish but it requires very few ,very small fish, with small feeding's every couple day's to prevent harm to the fishes.
Method I have used for setting up numerous classroom tanks, where children were not inclined to wait on empty tank to mature, does not work well with large fish,or too many fish,or too much food being introduced too often.
For a nice community tank of 75 gallons, I would first set up the tank,plug the heater in and set it for around 76 degrees and also place the filter in the tank as well, and let the tank run with no fish for a week to ten days.
I would then purchase four or five small active fish such as
Pristella Tetra's,Blood fin tetra's,Silver tipped tetra's or small danios.(not giant)
These are small active fish, and would represent small bioload for 75 gal tank. I would feed these four or five small fish a tiny amount of food ,about half a dime size amount of flake evry other day and no more.
After ten day's , I would purchase another four or five of these same fish to make a nice school and would leave these now eight to ten fish in the tank for another ten day's while feeding same small amount of food every other day.
I might then purchase three or four cory's and leave these fish for another ten day's while still feeding same small amount, and after the ten day's,,purchase another three or four cory's and leave them for ten day's while still feeding small amount like before.
Tank will now have been running for approx three weeks and i would perform at this time a 30 to 40 percent water change with fresh dechlorinated water treated with water conditioner such as PRIME and I would do this each week on same day from this time forward.
you have not been overfeeding so the filter material should be relatively clean and a healthy bacterial population is maturing there as well as on the surfaces in the tank such as the gravel,decor, wood,rocks,etc.
I might then select a centerpiece fish such as
Pearl Gourami,
Honey Gourami, or four or five
Platy's and begin feeding the fishes once each day no more than you actually see them eat in a minute or two.
in this way the tank will naturally mature(cycle) and there is little risk to the fishes for they have been introduced over a period of time, with chance for biological filter to mature between new additions of small fish.
There is no need for daily testing ,or frequent water changes if done as I described and fishes will not have been placed in toxic to lehtal condition's.
Any deviation from that I described, and all bet's are off with regards to the health of the fishes if too many fish ,too large of fish,too much food,or inappropriate fishes, are placed in this galss box of water.
Deviations are likely to result in sick ,dead fishes and toxic condition's which will affect all fishes added to the tank for weeks ,possibly month's.
Hope this helps.
P.S. You could add live plant's to the tank at any time during the process i described but adding them from the get go would be extra benefit to fishes and water qualtiy.
Another member here,Byron,,, would be the person I would contact about all thing's plant /fish related.
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