Orchid medium problems

[beckky]

Hello, I am back with another question and a very loooooong description
Some months ago I bought 3 orchids (phalaenopsis) from a local nursery. They looked amazing, one had 3 flower spikes with huge flowers. I was watering them once a week (they were potted in pine bark, I believe). Eventually they lost their flowers and I cut the flower spikes. Everything was going well until one of them started to get one yellow leaf, and then another and both of them fell. More leaves had the same issue and at some point she only had 3 remaining leaves and the stem was really dark. One day I wake up and found that the crown with 2 leaves just fell. It was the end for her.
(One thing that I noticed with these 3 orchids was that the roots never turned gray, they were always bright green, even when I didn’t water them for 3 weeks.)
I started to inspect the other two orchids and found that one had some sort of mold going up the stem and one leaf was already on the path to turn yellow. I decided to take it out from the pot and inspect the roots and that is when I found out that she still had her seed plug attached and all the roots in the plug or around were totally rot. I cleaned everything, I cut the black and mushy roots and left it without any potting medium. I also took the other orchid from the pot (she didn’t show any sign of sickness except permanent green roots) and found that she also had the plug and some rotten roots.
At this point I went to the nursery and took the orchid with me. The lady was very surprised to see the plug but thought it was ok ( I argued that it didn’t seemed healthy to have that old thing there and that the bark and the plug would dry out at different speeds and that could lead to root rot). After seeing the photos of the dead orchid she decided to offer me a new one ( a very healthy one, she said).
So.... now I have a new orchid, I haven’t water it since I brought her home (10 days ago), her roots are super bright green, it looks like there is some sort of green moss or algae in the pot and the bark in the surface has white specks and white areas that for me look like mold.
I have no idea what to do.
I ordered some good potting medium for the 2 orchids that had the plug, but I don’t know what to do with this new orchid (she is in bloom).
I will attach some photos to illustrate the whole situation.

[beckky]

Here are the photos of one the orchids that had the seed plug.

[beckky]

The new orchid photos

[estación seca]

The orchid you showed with the seed plug had healthy roots. Did you cut all of them off?

[Roberta]

You can easily remove most of the plug, bits at a time, with a tweezers. Whatever doesn't come off easily, just leave, won't hurt anything. Much better to leave a bit of old medium than to destroy roots trying get them totally "clean". Preserving roots should be priority one... and two and three... With an adequate root system the plant can tolerate, and recover from, many "insults". Without those roots, an otherwise healthy plant won't stay healthy very long.

[beckky]

Hello! No, I kept almost all of them. The rotted roots were the ones inside the plug, They were black and mushy, I just cut those off. I managed to remove the plug from both orchids and now they are waiting the new medium that I ordered (a mix of coco coir, perlite, charcoal, bark, zeolite...).
I can take a photo tomorrow (with daylight) of how the roots look now, I think they look healthy and happy to be free from that plug/old potting medium.
I am now concerned with the new orchid, is it normal to have white patches on the bark as well as green moss (or some other green substance in the pot)?
And is it normal for those roots to never look silver or gray? They keep that green colour always, even if not watered for 3 weeks. I don’t remember that happening with the other orchids that I had in the past.

[Roberta]

If that orchid hasn't been watered for 3 weeks and is still damp, the medium is very bad. When you get your new medium, repot that one too. Also remember, when the plant has fresh medium, it will dry out much faster and you will have to water more often. To know when to water, consider this approach: Water well, let drain, then weigh the plant on a kitchen scale or postal scale. Then weigh the next day, etc. When the rate of weight loss declines (not much more water to evaporate) it is time to water again.

[beckky]

Thank you so much for the tip, its a great idea to use the scale and weight it!
The new orchid is in full bloom, should I wait until there are no flowers to repot it?

[Roberta]

If you are gentle (don't knock the flowers around) Phals don't object to being repotted while in bloom. And since Phal blooms can last for months, in that time a situation with broken-down medium can turn bad, so don't wait. When you repot, just pick out the media that is easy to remove, don't try to get the roots squeaky clean. Rinse under running water to clean up the roots, then repot. It will appreciate the fresh, airy medium.

[Dalachin]

Are the plants kept warm and in good light?