quikv6

That looks like Columnaris, sometimes known as Saddleback disease. Follow Colu's advice above.

He looks amazing! Kudos for the dedication to treat him diligently, and also for posting the good news, which can be inspirational to others who look for guidance and a real success story. Well, well done.

0 KH is always a concern, as it could be resulting in a PH crash. For example, you measured it PH at 6.5. I am curious what the PH is out of the tap. It could be significantly higher, but can plummet and fluctuate due to 0 KH. That can certainly stress fish out and cause issues. If KH is 0 out of the tap, I recommend crushed coral as a start towards stability.

I feel it's important to know your GH and KH. The more you know about your water the better. When I was new to the hobby, I decided on the fish I wanted to start with, like everyone always suggests. (I picked Mollies and Platies) I knew nothing of my water, but everyone also says not to chase parameters, and that the fish will adjust. So I got the fish, and they did very poorly. As it turns out, my water was as soft (very low GH) as can be, with almost no KH either. Needless to say, I could see the fish struggling. I lost one, sadly. It was not until I tested my GH/KH that I realized what was "wrong." With no KH, I had the PH swing/crash. I immediately started doctoring my water, bringing up the GH/KH, and in turn....PH. The fish responded extremely positively. It was instantly noticeable, even to a beginner. Since then, I "doctor" my water, and do my best to create a good, stable environment for the fish I have. So when folks say not to worry about GH or KH....I would say you may not need to worry about them, but you don't know until you know what they are. I will also echo what others have said: Stay positive, learn, do your best to relax, and things will fall into place, yielding true enjoyment and appreciation.

You should measure the GH/KH so you know what it is, and also compare it to that of the store you got the fish from. If they're significantly different, that can be an explanation for the losses, and may require a different acclimation process going forward.

I also recommend getting the ammonia down to zero, and cut the Nitrates to 40 or below.

It does have both...but neither will be effective if it is wasting disease. You would need Levamisole (Expel-P), or other dewormers like Flubendazole or Fenbebdazole.

I believe temperature is very important. They are kept much cooler than tropical fish tamps. Low to mid 60s should be good.

Salt won't hurt them. I'd start w 1 TBSP/5 gallons. You can work up to 1 per/gallon if you really needed to, but that is pretty strong.

Being she responded positively to the salt (as most mollies would), I'd add some in the tank and observe.

Don't beat yourself up....issues always arise. How you handle the issue is important, and it sounds like you are on the right track. Wondershells will raise GH, and crused coral will affent KH (and PH, in turn.) Neither will case any ammonia spike. With livebearers, both are good ideas.

7 nitrate is very low. I dont even know how you measure that low. Do you mean 70?

Wondershells will only have a significant impact on GH. Crushed coral will help KH. They will not cause ammonia spikes.

For Fungus, API Fungus Cure is excellent. It may be tough to find though. There are also some bacterial infections that can mirror a fungus, which can make treatment difficult.

Hey SunniSki, It was a cycling issue prior, when you had shown .5 ammonia. Given it's an established tank, measurable ammonia over duration usually indicates a bump in the cycle, unless it is coming directly from your tap water. These things happen, unfortunately. I really doubt it's Paracleanse, as that should be Praziquantel and Metronidazole (parasite meds), and neither should have a negative impact on beneficial bacteria. I have personally used that med (as API General cure) many times, with no negative cycle impact. Also MetroPlex and Prazipro separately, as well. That doesn't mean it isn't possible, however. Maracyn has far more potential to harm good bacteria. (I can't remember if you used that as well). Regardless, going forward, good clean water can do wonders, along with some aquarium salt. Stability is key.

I'd try Maracyn 2, or Kanaplex. Either (but not both), by means of food mixture.

If I remember correctly, 10ppm was the lowest to visually see on the API nitrate test. 5ppm would be very difficult to see. Did you shake the bottle vigorously? After reading the above, you recently showed ammonia, and are not showing Nitrates (or barely). I still believe it is a cycling issue.

Without knowing if these guppies just came from drastically different water, I think salt would be a good idea.

You can also try Flubendazole. It is effective in the water column or food, unlike Fenbendazole, which should be in the food. I have found Flubendazole to be highly effective on wasting disease....moreso than Levamisole. It is more difficult to work with, and doesn't dissolve well in water. But it downright works.

salt will be fine, but you may need minerals. What are your GH and KH?

If he's not eating, I think Kanaplex may be a better med to use, rather than Erythromycin. Also, check that temp with a thermometer if you can, as those gauges on those topfin heaters can be off by quite a bit.

Looks like 2 potential issues: 1) Cycling issue: 0 Nitrates. Presence of ammonia. 2) KH (and GH) are a tad low for livebearers, which was discussed above.

What were your water parameters? It may have nothing to do with disease, and more to do with ammonia/nitrite, or lack of GH/KH. I'd look into all of those parameters first and foremost.

If you are cycling with no fish, there isn't a need to change the water.

It's also good to have some way to measure ammonia, as the multi-test strips don't measure that. They do have a dedicated ammonia strip, if you wanted to buy those. On a mature tank, I think it is less of a possibility, but given yours is a new tank, you can experience bumps in the cycle as it settles in.