Sick Molly - Help!

[bensfirstfish]

I have a new 125 litre tank, fully cycled and with stable ammonia (0), nitrite (0) and nitrate (0) levels, temp maintained at 26 deg C and a pH of 7.8. It has live plants, a bubbler, a terracotta pot, bogwood and sand substrate. I started with 4 dalmatian mollies and a bristlenose plec. All settled very well, the mollies feeding out of my hand and after a few days, one gave birth, resulting in 6 healthy fry (still going strong). 
 
Nitrates etc remained stable at zero for a full week after which I added 5 sterbai cories. The mollies seemed stressed about the introduction of their new tank mates and were considerably shier, but still active and feeding.
 
After a further 10 days however, I found one molly dead but with no sign of illness, fungus or parasite. A week on and now a second molly is looking lethargic and has obviously lost weight. She just sits at the bottom refusing to eat. She's not gasping or anything.
 
The rest of the fish seem fine - no gasping at the surface and all eating well. What's going wrong? I'm so sad to see my lovely mollies die off like this.
 
Any clues very gratefully received..
 
By the way, I feed them an algae pellet (for the catfish) before lights out, plus a few pinches of flake food for the mollies, plus a slice of courgette or cucumber, broccoli and the occasional green pea.

 

[phoenixgsd]

are you useing paper strips or a liquid based test kit? how exactly did you cycle your tank? when was your last water change? your readings of 0ppm for ammonia nitrite and nitrate suggest your tank hasnt actually cycled

 

[bensfirstfish]

I did a fishless cycling adding ammonia to 4ppm every few days after initial levels dropped to zero. It took about 5 weeks for nitrite to drop to zero once the ammonia converting bacteria had kicked in, and then a further week for both ammonia and nitrite to come down to zero within 24 hours. After a further week, nitrates were also reading zero. I'm using a liquid API test kit and I do a 25% weekly water change (plus general hoover round and algae clean). The other fish seem fine. I also have a silly number of snails - don't know if that can cause problems?
 
Hope you can help?

 

[bensfirstfish]

My sick Molly is still sick, but she hasn't died and everyone else seems fine. The temperature dropped to 24 deg overnight (one cold night) might that have cause some undue stress?
 
Also, I'm confused - why might readings of 0, 0, 0 suggest my tank didn't actually cycle properly? If the filter hadn't built up populations of denitrifiers, I would exppect big ammonia and nitrite spikes/high levels rather than consistent zero readings? Maybe I've got the wrong end of the stick?
 
One thing I have noticed though is the pH seems to be increasing. My tap water is high pH (about 8.0) but up til now the bogwood seems to have brought it down to about 7.4. But the last test showed a much higher reading (7.8 or so). Might this be part of the problem? If so, what do I do? I bought a pH lowering supplement but haven't used it because of the warnings that I might get sudden crashes whiich would be worse for the fish than acclimating to high pH.
 
My sick molly still isn't right, but she has at least now joined her friends in their resting place at the top corner of the tank rather than sitting on her own at the bottom.
 
Might the addition of the cories have cause them stress? Are cories and mollies not behaviourally compatible?
 
Still scratching my head.......

 

[Fishywonder]

Reading s of 0,0,0 would suggest an uncycled tank as Nitrate is the end product of the filtering process and the stuff that we dilute with water changes. I would not expect 0 reading on a nitrate test unless your tank was stuffed with real plants.

Can you say what testing kit you are using? The strips are unreliable, API liquid tests I have found to be the best but you have to really, and I mean REALLY shake the nitrate one up otherwise you get a false reading.

Your Molly maybe suffering from poor water, weaker fish subject to it quicker. Until you can get proper readings there is little more can advise, sadly.

 

[the_lock_man]

The OP has said that he is using the API kit, so I would suspect that the usual API nitrate bottle #2 problem is at play here. It seems to me that the tank is cycled, given that he was adding 4ppm bottled ammonia for 5+ weeks.
 
I can't really say what killed the molly, but I never really had any lasting success with mollies myself, I think you just need to chalk it up as "One Of Those Things That Happen". SOrry I can't be any more help than that.

 

[bensfirstfish]

Thanks both for your replies. Unfortunately my Molly died this morning. I still have 2 and now 8 babies which all seem ok as are the cories and BNP. 
 
I'm pretty sure the tank is cycled as I recorded a drop in ammonia from 4ppm to zero, then a spike in nitrite (that went off the scale). Then both came down to zero reliably within 24 hours. I'll have another test of everything (yes, I am using the API kit) when I get home tonight and I'll make sure I give bottle #2 a really, really good shake.
 
Friday is water change day, but I'll maybe do it tonight along with a really good clean up.
 
I do have a lot of live plants in the tank.
 
Thanks again for your help and I'll post the test results later on today. Any more ideas from you guys or anyone else, very gratefully received as I got pretty attached to my mollies - they are very personable, friendly fish and it's sad to see them poorly.

 

[bensfirstfish]

OK so after some very vigorous shaking, nitrates look like they might be at about 2ppm (not as yellow as zero, but not as orange as the next category at 5). I've done a big water change (maybe 30-40%) so hopefully that will help. I have been changing the water every week, but maybe I should be doing it more frequently? Or am I maybe feeding the tank too much? Would 2ppm nitrate be enough to kill my mollies?
 
Thanks for your help.

 

[the_lock_man]

2ppm nitrate will not do any harm to anything anytime. You only want to start being concerned about nitrate when it hits 3 figures!
 
Just to clarify a bit of an issue with the above - 0,0,0 results are what you might expect in a tank that has just plain tap water in it and no fish. Even then, quite a large proportion of the planet has nitrate in its tapwater (eg, I have somewhere between 30-40ppm coming straight out of the tap). In an uncycled filter with fish in the tank, although you might see 0ppm nitrate (assuming you have 0ppm from the tap), you most definitely would see ammonia and/or nitrite.
 
In terms of a nitrate reading, a decent enough reading is anywhere kinda 20-40ppm ABOVE what your tapwater reads. But I still reckon you're not shaking that ******* bottle no.2 enough. The ingredient that does the actual reading of the nitrate (the reagent) is a powder, which can, and often does, precipitate out of the solution. Unless you get that powder totally dissolved again, you're not going to get viable readings.
 
But in any case, it's still unlikely that this is what nobbled your mollies (Gawd, that sounds like a euphemism for something, but let's not go there.....)
 
And unfortunately, I still can't get any closer to what did. It may be that you just got sold a particularly weak batch.