Have lost almost all my fish over 10 days, gutted :(

[Marne]

Over the last 10 days my fish have been dying ( a couple each day ), my tank is now almost empty apart from fry. 2 weeks ago I added some more sand to my tank so I could plant some plants, I added 4 plants from my local aquatic shop and 2 moss balls bought from ebay. My water has been testing fine other than my nitrite being 0 ( think that's the right one ) ammonia is 0 and my ph is a bit high ( but that's always been the case ), fish have showed little sign of illness and go down hill very fast, I have lost my rainbow shark, 2 panda Corrys , 3 swordtails, 3 mollies, 3 guppies and 2 neons, my plecs are all ok but looking stressed. I have been doing lots of water changes, have been moving the sand around ( in case there's any gas build up ), have air pumps running but fish are still dying.

I'm now thinking I'm just going to have to sit back and see what happens, if all the fish die then I can scrub the tank, clean everything and start again , totally gutted.

Oh Marne :( I wonder if you've got a really stubborn strain of mycobacteria in there. Stripping down and scrubbing would be your best bet.

Did you smell anything when you moved the sand around? How high is the pH? NitrIte and ammonia being 0 is good, what about the nitrAte? What kind of sand did you add?

Ph is around 8 but the lowest it has ever been is 7.5 ( so no huge change ), couldn't smell anything when I moved the sand around ( I don't think it's been in there long enough to develop any gas pockets and my bottom feeders are quite good at turning it over), just found another tetra dead , all I have left is 5 tetras, 1 lonely Molly, my bandit Corrys, a couple guppies and my plecs ( and a load of guppy fry but I may have lost some of these as I'm not sure how many I had ). The swordtails were poorly anyway after they went skinny a few weeks ago but I only lost these yesterday after doing a water change which seemed to finish them off, everything that's left seems healthy other than my plecs who look stressed ( colour shave faded on them ). I'm going to try and find a small tank and start cycling it, then I can move anything that survives into there when I clean down and cycle my big tank. I'm collecting rain water in hope I can use it to lower my ph, I have tried buffers in the past but they don't work , I'm gutted, have probably lost around £30's worth of fish, doesn't sound loads but it's quite a lot for livebearers and Corys.

The sand was plays and, the same as I had in there ( argos play sand ), spent hours washing it, I lost 2 fish before I added the sand so it's quite possible that there was something going on before I added anything, I just thought these had died of old age, I have lost 3 fish today and wouldn't be surprised to loose more. Water changes don't seem to be making any difference.

What's the nitrAte level?

Nitrate and nitrite are 0, ammonia 0

WEird. I think if it is a mycobacter infection then moving the fish to a new tank won't help. Have you tried antibiotics yet?

Don't use rainwater for lowering the pH, it can carry pollutants. Use RO water, you can either buy it or get your own machine. Then you'll need to add the right minerals to make it up. I wouldn't mix up hard and softwater fish, just stick to one or the other and give them the water params they need.

Fingers crossed for your remaining fish :(

I have treated the tank for disease ( can't remember what treatment I used now ), was told rain water would be ok as I live in the middle of the countryside ( no pollution)? I have been testing it first. I have a RO unit but not enough room to set it up, the nearest place I can buy it from is 30 miles away ( a bit of a pain )

I will just have to let whatever it is run its course, I just hope I don't loose my plecs ( they have survived many things), once things have settled down I can start again, maybe with something that is happier in hard water?

I wouldn't use rainwater, even in the countryside. I know a lot of fishkeepers used to but I wouldn't risk it.

Yes, matching fish to your tapwater would be much less work. I'd test the pH over a period of time to check if it was fluctuating a lot as well.

Havn't lost any fish today ( first day for a while ), all fish looking ok so hopefully we are overt he worst. Tank looking a bit bare though and will be quite a while before I can re stock.

That's good news! Hopefully this means things will improve now.

Yes, definitely leave a few months before you restock and make sure you quarantine new fish so that you don't get any further problems.

I'm going to concentrate on planting the tank whilst it settles down ( spend money on plants and moss rather than fish ). Even my plec is looking better ( back to his normal colour ).

Lost my last mollie today , she was perfectly fine last night and dead when I got up.

Oh no :( Are there any visible symptoms at all?

Nothing Eau, that's the annoying thing, the swordtails I lost were already poorly so I think what ever this is finished them off, this mollie was very healthy, happily swimming around and fed well last night so was shocked to find her dead, other than the skinny swordtails one of the others have really shown any signs of illness .

Lost more fish , have taken all my bog wood out and the fake plants ( so I can see any fish that die nod get them out as fast as I can ), have also set up a 2nd filter to circulate the water a bit more and incase the other one is not working properly. I'm down to guppy fry, swordtail fry, 3 adult guppies, 3 bandit Corrine's and my plecs, have no adult mollies or swordtails left .