Alright, so I did another 20% water change on Sunday. The water has stayed clear, and the fish are all looking healthy. I still struggle with the pictures, I'm too old, idk what the deal is. but here are all the questions that I can answer. I am still nervous that I am on a strange delicate balance of like, things look good, but there is still a bacteria or something kind of problem
Tank size: 10G
pH: (per water report) 7.7-7.8
ammonia: 0 - tested myself. This has been at zero each time I have tested as this issue has been going on
nitrite:
nitrate:
kH and gH: (per water report) I'm not 100% sure how to interpret what the report says, but it lists under hardness 119-125ppm and 7-7.3 gpm
tank temp: 78 degrees farenheit
Here is the link to the site with the water report. In the first paragraph on the right side Consumer Confidence Report. The link is in that paragraph "current 2019 report" links to a pdf
Fish Symptoms (include full description including lesion, color, location, fish behavior): currently all fish look ok right now. Looking at the information in the link about dropsy, that looks exactly like what happened
The first fish, had been having drooping kinda raggid looking fins for several weeks, then I started to notice the pineconing that developed slowly worsening, he started resting on the bottom during the day when the pineconing happened. Slowly I started to notice that the back of him seemed like it was swelling and he looked like he was stiff, and unable to move his tail fin appropriately. Then everything kept getting worse until he passed, hardly able to swim at the end
The second molly that passed away didn't have nearly as many symptoms other the one. Her fins started to droop about two days before the other fish passed away. The last day the first fish was alive this second fish started resting on the bottom. I never noticed any pineconing or swelling for her. She went from drooping fin and resting on the bottom and the next morning she had passed (two days after the first one).
That evening I noticed that one of the corys was scratching his side down through the sand a few times, not obsessively, but maybe 3 or 4 times within about 15 min that I sat and watched.
After I did the recommended 75% water change, vacuum and clean out. (I now have one remaining molly and 3 stebari cory cats in the tank. The molly was born in our tank is about a year and half. Two of the corys were purchased and we've had them for over 3 years. The third cory we've had for about 2 and a half years) they all appeared stressed, and the poor molly was schooling down with the corys, and they were all staying very hidden. However after the water change everyone looked physically healthy and moving in all the correct ways, fins and gills looked good (I thought that maybe the corys gills looked a little bit more red than normal, but I also had been staring at and obsessing about everyone constantly, so I don't know if this was actually the case or not.
Starting the next afternoon everyone's behavior was back to normal, the molly came to greet me at the side of the tank when I walk by in the morning (they all used to do this together, I love it, they know where their food comes from I guess lol) and he was back swimming around on the top levels as opposed to hanging with the corys.
Volume and Frequency of water changes: I do about a 15-20ish% water change every sunday, occasionally I will miss a week, but not often. I try to do a slightly larger amount of water the next time.
Chemical Additives or Media in your tank: I haven't put anything in except for fresh water since the second fish died. Normally all I use is a dechlorinator, when the first fish started having serious issues I started adding the pimifix and melafix treatments.
Media in the tank is sand at the bottom, two low silicone plants, one plastic plant, and a few taller silk plants. I have a bridge ornament thing, and a thing that looks like a beechwood branch, but its not real wood - its the same material the bridge is made out of, and then I have a large flat rock that I have propped against the wood to make a cave type thing. I also have one of the "beta logs" that is an ornament that floats around the top and is basically just a tube they can swim into.
We have a small amount of green algae that builds up on the glass, and you can see it against the glass down in the sand area, but it's only up against the glass where the light comes through, and not like all over the tank, I scrape this off every month-ish, sometimes every other week, depending on the time of year the tank gets a little more or less sunlight (not direct sun, just makes that part of the room brighter). I get a little bit of a more brownish I assume to be algae that builds up on some of the plants and ornaments, I will rub that off of them maybe every 3-5 months, it doesn't get out of control, just kinda discolors them a bit.
Tank inhabitants: Currently I have one molly, and 3 stebari cory cats. I used to have two other mollys that recently died
Recent additions to your tank (living or decoration): just the beta log - I added this when the first molly started struggling because he was resting down on the bottom, and I thought he might like a resting place that was closer to the surface, and he would occasionally sit in the log. Before adding the log I made sure to rinse it thoroughly and I have a fish-tank-only toothbrush that I use to scrub things off of, and I used this as I was rinsing it. I did not use any soap of any kind.
Exposure to chemicals: The only things are the pimifix and melafix that I was adding. Nothing otherwise.
How do I know if the problem is solved or if there is still bacteria or whatever in the tank just slowly making things sick that I can't see yet?
In an earlier post we talked about what might be mixed down in the sand. I have about 1-2 inches based on where in the tank. I have to make heaps to keep some of the plants down. I didn't stir or mix it up when I vacuumed, I just did the very top layer. Should I go through and kinda mix everything up? or if there is something growing down in there will that just let it loose and I need to move the fish first?
So if you’ve the cash then you can splash out on these 
