Hello everyone... I'm Finally ready to jump in the water

Hello APC Community!

After researching and collecting supplies for many years, I'm finally ready to start my first planted aquarium.

I've been on APC for awhile now and have posted questions in the past but I never posted an official introduction.

I've had a 44 gallon fish only aquarium for alomst a year now as I was saving up for various pieces of equipment that I would need for when I started a planted aquarium. I also have a 55 gallon tank that I plan on setting up as a planted aquarium, possibly an igwami. One of the reasons it has taken me so long to get started, was that I was buying supplies for both tanks at the same time. I've decided that this is taking way too long and I am going to concentrate on one tank at a time.

I'm setting up the 44 gallon first. (my journal of this build will follow soon)

I've torn the tank down and moved my school of tiger barbs to the 55. It took me alot longer than I expected to paint the back of the 44 gallon black. I saved about 30-35 gallons of the tanks original water in plastic tubs, but they have been sitting there, unfiltered for about 4 days.

Is this safe? Should I use this water or should I just transfer water from the 55 gallon that they are currently in? The water in the 55 gallon is cycled and the filter is mature. However, if there is no problem with the water in the buckets after 4 days, I'd rather just use that and keep the 55 going with mature water so I can use it as a quarantine tank.