Fish losing rear fins

[jdsolo]

I just added 4 guppies to my 20 gallon tank last week. Previous occupants were four zebra danios and five neon tetras.

Danios seemed a bit aggressive. I have had two guppies, two tetras, and one danio turn up dead with their rear fin gone. Very wierd. Is this due to aggressive behavior?

I thought these fish were community fish and are similar in size.

Any thoughts or suggestions?

John

[mt_marcy]

Hi,
Yes guppies, danios, tetras, ect. are cummuntity fish and should get along okay. Before the rear fins fell off, were they ragged? If so, then maybe they suffered from fin rott...what are your water conditions/perameters(levls)? Have you tested your water? If not, then maybe you should...Let us know more info on your tank, as that would better help us, to help you. Good luck,
mt_marcy!

[jdsolo]

I didn't notice any fin rot.

I've got a test kit. Water conditions are 76 deg F. pH around 7.0 - 7.5. No nitrate or ammonia levels (reading near or at zero).

I do have hard water (200 ppm) from the tap. I have used a softener pillow before but don't currently have it in the tank.

John

[PumaWard]

What are your nitrite readings?

I wouldn't bother using the softener pillows, all your fish can handle your water and the guppies prefer it. The pillows don't affect gH anyway (they lower kH, not good! :) )

[aquariumfishguy]

It seems strange to me that your nitrAtes AND ammonia levels are at zero. And I would also like to ask, what are your nitrite levels. It almost sounds like your tank isn't cycled, except that usually if nitrates aren't coming up, ammonia sure does. ;)

How long has this tank been set up, and was it properly cycled?

[jdsolo]

I was not correct earlier. Nitrite and ammonia are zero. I don't have a test kit for nitrate.

Tank has been active for about 18 months.

John

[aquariumfishguy]

ok, well in that case your tank is probably cycled unless your test kits are providing false negatives. Now you need to go get some nitrate test kits so you can see just how high those are. Excessively high nitrAtes can cause fin rot (tail rot) and it makes for (in general) poor water quality. The only effective way to rid your tanks of nitrates is to do many water changes. Make sure your doing partial water changes every 7 or so days.