Fin rot and lethargic yet again

[Irksome]

I have had this happen a few times recently as some of you have already advised me and I appreciate any help and advice. My toxin levels have finally stabilised and my overly ambitious stock reduced to a more sustainable level, (7 male guppies in 10 gallons), I’ve added many more plants - anacharis and water sprite, I feed every other day. One of my poor fish has once again deteriorated. I have been trying to treat his fin rot for weeks with water changes and Melafix. It has visibly worked well for the two others who had fin rot including one who has grown back a large bite out of his tail without trouble. this poor guy has just been getting worse, along with his tail rot he has been losing weight and energy and can barely support the weight of his own tail in the water. now he is taking frequent rests on the substrate. I do water changes twice a week but he always seems much worse after the stress of the water change so if possible I don’t want to be doing them every day again. I don’t understand how the treatment could work on the others but not him. The other possibility I have pondered is that I bought my stock from two different sources, all the ones that have weakened have been from the same breeder and all had big tails and cobra patterning. All my very healthy looking fish are round tails, brightly coloured but not so fancy. Should I find a stronger medication or change my maintainance schedule? Are the positive effects of the new plants just taking time to kick in? Has anyone actually had a guppy make a full recovery after they have been lying poorly on the bottom of the tank? How likely is it to be genetics and not my care compounding the problem?

 

[Essjay]

Do you have hard or soft water?

It is possible that some of the fish came from a less than healthy stock. But if you have soft water that will weaken even more because guppies need hard water.
Could you look on your water company's website and do a search for hardness please. You need a number and the unit of measurement. That will help us work out whether the water hardness is part of the problem or if we need to look elsewhere.

 

[Irksome]

Do you have hard or soft water?

It is possible that some of the fish came from a less than healthy stock. But if you have soft water that will weaken even more because guppies need hard water.
Could you look on your water company's website and do a search for hardness please. You need a number and the unit of measurement. That will help us work out whether the water hardness is part of the problem or if we need to look elsewhere.

My water is hard/very hard I think. For a while I had the pH of my tank at 7.5 but it recently jumped to above 8. My water test kit gave a reading of KH9 or 160mg/l. My test kit gave a GH reading of 16, or 264ppm My water company gives a reading of 19 degrees Clark, I don’t know what a Clark degree means.

 

[Irksome]

My water is hard/very hard I think. For a while I had the pH of my tank at 7.5 but it recently jumped to above 8. My water test kit gave a reading of KH9 or 160mg/l. My test kit gave a GH reading of 16, or 264ppm My water company gives a reading of 19 degrees Clark, I don’t know what a Clark degree means.

I just worked out that GH means German hardness. My water supplier has that as 15.26

 

[Essjay]

GH means general hardness. German degrees are also called dH. Clarke degrees are also known as English degrees. There are at least half a dozen units which can be used for hardness.

There are two units used in fishkeeping - dH (or German degrees) and ppm (or mg/l calcium carbonate).
Your hardness in Clarke degrees converts to 15.2 dH (as your water supplier says) and 272 ppm. And your test kit is pretty accurate too.

Your water is hard, and it is fine for guppies. So we can rule that out as a cause. Since the ones with problems came from one supplier, and the ones not having problems came from a different supplier, it does suggest that one batch of fish is unhealthy for some reason.