Black Patches On My Guppies Tails?

[Fraoch]

Hi, Ive had my tank for about 4 months now and about a month ago i added 6 female guppies and 2 male guppies to the tank which already had 2 platys and 2 black neon tetras in it. Not long after i added them, my black male dissapeared and when i checked the tank i couldnt find him so i can only assume that he died and the other fish ate him.
About a week or two later my snakeskin female guppy also died 2 days after i found one of her pectorial fins was sticking straight out from her body and was white adn she couldnt move it.A day later she died suddenly.
Then about a week ago i noticed all my platies and guppies were flicking and rubbing themselves on the gravel in the tank. I looked into this and decided to treat them for whitespot a couple of days later.After that they stopped rubbing and flicking and acted normal.

Now 3 of my female guppies tails have turned black at the base and one has streaks on the tip of her tail aswell. 1 of my platys has had some of her scales turn slightly darker aswell. Is this normal for them to change colour now and again? Or is it something to do with the treatmeant i gave them?

I also ordered some new fish from an online store a while back and they took some time to get the fish in stock and now should be arriving tomorrow. So now i need to no whether to put the fish in the tank or what to do with them as i dont have another tank?

Sorry for such a long post but i thought you ould like to know the background.
thanks fraoch

 

[CTGoldfish]

IT could be fin rot starting but I am not completely sure,or a fungal infection could be something simple as ammonia burn
What are you water parameters,the size of your tank would help a lot
Have you cycled your filter?

 

[Fraoch]

IT could be fin rot starting but I am not completely sure,or a fungal infection could be something simple as ammonia burn
What are you water parameters,the size of your tank would help a lot
Have you cycled your filter?

well heres a picture of my yellow female, she has the black at the base of her tail and on the bottom tipView attachment 61422

its a 70 liter tank and the filter hs been cycled. I used a test strip and it said that they're was no nitrite/nitrate, GH was between 6 and 10, KH 3 and PH 6.8.I dont have anything for ammonia, should i get one?

 

[CTGoldfish]

that looks completely normal to me
I'm not sure if guppy patterns could change but if they can yours might have
and as for an ammonia testing you should keep something to test it with
if it is something bad it would be ammonia burn but some guppys darken with age (just looked it up) also some change during the breeding period

 

[OldMan47]

The female in your picture looks quite normal, no problems that I can see with any common disease. What I do see is that you list no nitrites and no nitrates. That is very unusual in a cycled tank. All waste that your fish produce, not just from their feces but even from respiration at their gills, will become nitrates after the mature filter processes them. Unless you are doing huge water changes quite often, I would expect a serious build of nitrates after 4 months of fish. At the very least, you could expect some nitrates, even with an aggressive water change schedule. That means to me that your test is misleading you to believe that your water is better than it really is. You need to measure ammonia levels in the water, preferably by using a liquid test kit like the API testing kit with the little test tubes in it. In general, I would use a liquid test to measure not only ammonia but nitrites and nitrates as well. The zero nitrates tells me your present test method is far less than reliable. With the 3 degrees of KH and a pH of only 6.8, you may get away with slightly more ammonia than many of us can, but it means that nitrites are even more dangerous than they would be in my high pH tank water. Your buffering capacity, as indicated by the KH, is very low and might even be called dangerously low by some people.
You might want to try measuring the pH and KH of your tap water. If it is higher than the tank water, a very large water change with adequate dechlorination might help you get your tank water back to values that are well tolerated by guppies. Although guppies are as tough as nails in my tank water, my KH runs over 10 degrees and my pH runs at 7.8, not 6.8. Guppies are typical common livebearers that do best with high mineral content water that would naturally have a pH of well over 7.0.

 

[Fraoch]

The female in your picture looks quite normal, no problems that I can see with any common disease. What I do see is that you list no nitrites and no nitrates. That is very unusual in a cycled tank. All waste that your fish produce, not just from their feces but even from respiration at their gills, will become nitrates after the mature filter processes them. Unless you are doing huge water changes quite often, I would expect a serious build of nitrates after 4 months of fish. At the very least, you could expect some nitrates, even with an aggressive water change schedule. That means to me that your test is misleading you to believe that your water is better than it really is. You need to measure ammonia levels in the water, preferably by using a liquid test kit like the API testing kit with the little test tubes in it. In general, I would use a liquid test to measure not only ammonia but nitrites and nitrates as well. The zero nitrates tells me your present test method is far less than reliable. With the 3 degrees of KH and a pH of only 6.8, you may get away with slightly more ammonia than many of us can, but it means that nitrites are even more dangerous than they would be in my high pH tank water. Your buffering capacity, as indicated by the KH, is very low and might even be called dangerously low by some people.
You might want to try measuring the pH and KH of your tap water. If it is higher than the tank water, a very large water change with adequate dechlorination might help you get your tank water back to values that are well tolerated by guppies. Although guppies are as tough as nails in my tank water, my KH runs over 10 degrees and my pH runs at 7.8, not 6.8. Guppies are typical common livebearers that do best with high mineral content water that would naturally have a pH of well over 7.0.

I have just bought an API liquid testing kit, i was always doubtful when i tested the water with my current tester and i will post my results when i get the kit