I'm Out Of Ideas And Need Some Help

[albita]

My fish keep dying and I don't know why. I'm starting to get really frustrated. My current tank is fully cycled and has been up & running for a couple months now, but my fish keep dying and I don't know why.

The tank: 36 gallon bow front
Stocked: 4 Zebra Danios, 2 Dwarf Gourami, 3 Mickey Mouse Platies. 
Temperature: 77-78 degrees (I can't get it cooler atm based on where I live)
Ammonia: 0
Nitrites: 0
Nitrates: about 10
ph: 7.8-ish.
I do weekly water changes of about 30%
Filters: Penguin Biowheel 200 & Topfin 20


I plan to add to the stocking list, but since my fish keep dying (thus the only 4 danios), I haven't been adding any recently until they stop dying.

When my problems started: I got a sick dalmation molly and didn't have a quarantine tank.  I didn't know it was sick when I bought it.  I treated the tank, which killed off a bunch of my healthy fish and caused a mini-cycle. I cleared out the medicine....got my few remaining fish healthy again and slowly added a few back in.  I changed tanks from my original 20 gallon to the 36 gallon about 6 weeks ago. But I am still losing a fish every week or two. One at a time. Some of them linger for a few days....others seem healthy one day and are dead in the morning. I was replacing them...which is why I still have fish...but I have stopped doing that now.  My water parameters all test out fine (using API liquid kit) and there is virtually no debris in the substrate at all.

So far, I've lost (in no particular order): 2 zebra danios, 2 dwarf gouramis, 3 dalmation mollies, 2 balloon mollies, 1 catfish, and I'm pretty sure I'm about to lose a platy based on her appearance this morning. No...they weren't all in there at once, I just kept replacing them. Seriously, it's one at a time.

Does anyone have any ideas? Because I'm out of ideas.  I should note that I also keep African Cichlids in a 55 gallon tank and have had absolutely no problems with that tank.View attachment 71927View attachment 71927

Thanks in advance! 

 

[FishGuy2000]

Do you use dechlorinator when you ad water ?

 

[albita]

Yes.  I use Prime. 

 

[Tongue_Flicker]

What was your fish's sizes when you bought them? It is possible that you've bought full, matured adults so that's why it was their time already?

 

[albita]

I suppose in theory, that's possible...they were definitely not babies when purchased...but some were juvenile size (unless, I guess, they could have been stunted?)...but I've now lost 10 fish, and 1 currently is not looking so good.  Of my original fish, there are only 3 danios left.  Kinda seems unlikely to me.

 

[FishGuy2000]

maybe a decoration in your tank could be putting something in the water thats killing them

 

[albita]

Any likely suspects?  Everything in the tank is from the fish store.  Rocks (non gathered, all purchased for use in aquariums), wood & plastic plants (and gravel substrate).

 

[FishGuy2000]

im not sure all the decorations i use ( besides sand and backgrounds ) i get from lakes or streams

 

[TwoTankAmin]

My hunch is you have what I refer to as a "tank of death" almost everything you put in dies. You treat the tank with a variety of things over time and nothing seems to work. What makes it worse is you see no external symptoms to give you a clue. If you knew somebody in a university ichthyology dept. they could take smears, autopsy dead fish etc. and likely figure it out.
 
Another option is to try and ride it out and eventually hope it stops. I had a tank like this years back, it killed a few 100 fish (many were fry). It eventually (in about 2+ years) fixed itself. I have no idea how nor what was the cause.
 
If this ever happened to me again I would simply break down the tank and would bleach everything that could withstand a decent bleaching and could be reused. I would rinse it all well and let it dry out. Then I would restart the tank from scratch.
 
The problem here is the fish still in the tank. They may be resistant to the underlying cause and still be carriers. They may have the "disease" but be slower to succumb. I hate euthanizing fish, but since it is only 4, this may be the only realistic option. If you simply keep on with them and then down the road try to add fish, you may be right back in the same situation of losing them fast. It would be wrong to move them into another tank where they might introduce the problem. So you really only have two options - dedicate the tank to these four fish and do nothing else or else euthanize them.
 
If you want to ride it out as things are, one warning. I would get separate nets, etc. to use on the sick tank and would also work on all other tanks first when you clean your tanks and do it last so as not to transfer anything from the sick tanks to healthy tanks. This would include putting your arms into the sick tank and then into a healthy tank.
 
You can try and figure out what is wrong and fix it, but with no symptoms only rapid death, anything you try would be a crap shoot. The only way you would ever know if it worked would be to add a new fish that you are as close to 100% sure is very healthy. If it dies you know the problem isn't fixed. That is a hard way to find out though.
 
If anybody has a better idea here, please suggest it because this is the best I can offer base on the information.

 

[albita]

In a weird way...having it referred to as a potential "tank of death" kinda makes me feel better.  Strange, I know.  But, seriously, it's been driving me nuts and I feel like I've tried everything.  Right now, there are more than 4 fish in there...just only 4 ORIGINAL fish.  I haven't had a death in about a week now....so I guess I'm due

.  The platy that looked sick still looks sick, but is now eating again, so might have beaten whatever it is?  Idk.  I think I'm going to wait a month or two to add anything new and see if the ones in there make it.  If they keep dying, I'll probably just wait them out.  I don't think I can bring myself to euthanize them.  Or, maybe set up a new, smaller tank for just them and start over with my bigger tank. That way they can live their lives out.

Question:  I have drift wood in there.  I'm pretty sure bleaching it would be a bad idea.  Would boiling it for a few hours so that the interior gets hot work to sterilize it if I end up having to go that route?

Oh...and I do have absolutely everything separate from this tank.  I started that early on when I started getting so many losses.  The tanks share nothing.  Except my arm.  Which is an extremely good point about being careful.

 

[TwoTankAmin]

Boiling wood will work. So should nuking it- but this may burn the wood if one is not careful.
 
Bleaching may discolor the wood. However, if one bleached wood it merely need to dry out 100% for tthe chlorine to b gone.
 
Albita- my tank did eventually right itself, after many many deaths. So it can happen. If you want to try and ride it out, just don't add any more fish untill its crystal clear the dying has stopped. I would want to see 6-8 week minimum with no deaths and longer is better.

 

[albita]

Yeah...I'm going to ride it out for now.  But, if it is still continuing by Christmas, I think I'll probably move them to the smaller tank so I can start over.  Heck...if it's still continuing by Christmas, I may not have any fish left anyway....  I'm still hoping that maybe whatever it is, is done.  Or almost done.  I guess time will tell.

 

[albita]

So, it's been 3 days since my last 30% water change. I just tested my water and got the following:

Ammonia: 0
Nitrites: 0
Nitrates: 5
Ph: 8.2 

Could there be something in my tank raising my pH or causing it to fluctuate that could be causing my problems? My tap water is 8.2...but to keep the fish tank lower, I had been mixing RO water with my tap water to keep it what I though was a steady 7.8ish (1 gallon RO to every 2 gallons tap). Clearly, it's not mattering if the tank is testing back at 8.2 a few days later or is something in the tank raising it. Thoughts? Could pH be my problem?