Am I overthinking or paranoid?

[bobaguppies]

I might be paranoid or overthinking that animates have sold me sick guppies.. it all started from February 4th when I bought a bag of female guppies. The tank looked vibrant, then the week after a guppy died. I thought it was complications from giving birth cause a couple of them came to me pregnant. But from there every week I start loosing 1-2 of them. It's all from animates, I got worried that something was wrong with my tap water (maybe it was double chlorinated and I didn't know?) but it didn't make sense as I have 6 tubs of aged water running for water changes and just to be safe I'll add some prime. I also bought RODI just to be safe during this but nothing changed. I religiously clean my tanks every Sunday and do a 15% water change, before it I'll do a test and Ill also do one after (I know I don't need to do this extra steps but I just have a major OCD so everything needs to be 'perfect'). All of my other tanks are fine, this is just from one specific tank for female guppies.

It's been 6 weeks, I had 12 female guppies and now I only have 4 (one is going through the same problem. They would have normal looking bellies and couple days before they die, they would get very very skinny for some reason). I've tried what the staffs have recommended me, salt, pimafix, melafix, meth blue nothing worked. Im at my wits end as all im seeing is a floating fish every Tuesday or Wednesday (is this a coincidence?). Idk what to do, I regret introducing new fish in the tank and should have been happy with my originals, they're still surviving but I think whatever it is in there, it's getting to them soon as a few of my originals are starting to show signs. Did anyone go through this??? Should I just cull the rest of them? It is sad that they're going through this and I can't do anything. 

[Caryl]

OK, so if I am reading this correctly, you added the new guppies to an established tank that already had fish in it and it is just the new guppies that are dying and not the originals?

What is a possibility, is that your originals have some sort of "bug" that doesn't bother them but the new fish have not encountered and so don't have an immunity to. Once the new fish started getting sick, it increased the number of "bugs" so now the originals are having to fight the larger number.

People always say you should quarantine new fish for 4 - 6 weeks to check they don't bring anything with them but that doesn't help if it is a case of something the fish have not built up resistance to. I had a similar problem once, many years go now, and it was not the fault of the fish shop. From memory, we just had to wait to see which ones survived. I don't think adding further meds to the water will help. Survival of the fittest.

Do the sick fish have stringy poo? That can be a sign of internal parasites.

Next time, quarantine new fish to check they are fine before adding them to the established tank. If they were sick to start with, they would show signs in the quarantine period. If they don't show signs of sickness until a week or more after being added to another tank with current inhabitants, I would look at something in that tank that is the problem. Not necessarily poor water quality, as it sounds like everything is good there, but something new to that particular batch of fish.

Someone else may have other suggestions.