Sick fish, no signs

[Ruby159]

I have a 40 gal tank of swordtails, I bought 8 online. They’ve been robust and beautiful. Ordered a second batch of 8 but it seems they were not as robust and healthy some have really not grown at all they are fed flake food frozen blood worms and a snak of algae tabs, this batch were pretty small when I got them. I added about 5 swords later on and all have been healthy. Later on one of the swords got a cotton looking growth in her gills, I quarantined her and treated with antibiotics that didn’t work. Tried malachite green, that didn’t work and she died. Now about 3 weeks later there are about 6 babies that were born here and did great, it seems now that they are all sick, there is nothing obvious. I’ve used a magnifying glass to get a close look, .Theydon’t want to eat and just kind of waste away. None have died. Ammonia 0,nitrites 0, ph 6.8, nitrates 5. I treated whole tank with para guard using only 3 caps instead of 4 as directed. It seems the fish are not doing well with it and look worse now. So I did about a ten gal WC.. I’m very frustrated and sad. I’m going to remove the sick babies to quarantine. Help! I feel like a failure

 

[Delapool]

Were the babies from the sick sword? Might be just a poor batch.

 

[Ruby159]

No everyone was fine and healthy, babies were robust. I’m beginning to think it may be the 8 swordtails that I bought online. Oddly a few of them have really not grown at all. Even though I feed the a varied diet, clean water, good parameters, I’ll remove the rest of them to quarantine and Medicate.

 

[Potluck]

No everyone was fine and healthy, babies were robust. I’m beginning to think it may be the 8 swordtails that I bought online. Oddly a few of them have really not grown at all. Even though I feed the a varied diet, clean water, good parameters, I’ll remove the rest of them to quarantine and Medicate.

Some fish take longer to grow than others, I have 2 kangaroo creek rainbows that are growing more slowly than the others they are a little over a month old and are still only about 1", the female is about 3/4.

 

[coralbandit]

I would look to the pH of your water.
6.8 is a little low for swords..They like /need hard water..
My pH is 7.6 and I still add 'wonder shells' to their tanks to supplement the minerals they need from the water...
https://www.amazon.com/Weco-Wonder-...&qid=1515376520&sr=8-1&keywords=wonder+shells
The infection sounds like a fungus issue. Do any of the fish have soars or injuries?

 

[flitabout]

I am wondering if it isn't columnaris. Ditch the malachite green and go with methalene blue, kanaplex nitrofurazone. That said I just came out of columnaris so I see that first.