Losing fish

[Country joe]

I've been losing fish, in the past week I've found two Rummy Nose Tetras dead, just bought in, and two neon tetras, which I've had for a year, all these fish have no marks on them, and no sign of disease, my two hundred litre tank is well oxinated with a Fluval 407, my temperature is a constant 24 .4 C.
My readings are ammonia nil, nitrite, nil nitrate, nil, PH 7.5, general hardness 8,
And Carbonate hardness 5.
Cant figure out what is causing these deaths, I have no aggressive fish, just small tetras, Harlequin Rasboras, and clown loaches and Ottos.i do 25% waterchanges weekly. And my testing kit is NT Labs.

 

[fish48]

take a closer look at fish to make sure there's no sign of white spot.
do a 50% water change t is more beneficial to do a 50% water change weekly.

 

[EmmaS]

Is it possible you did a water change without adding declorinator ? Added anything else to the tank? Ie plants, decorations, chemicals etc? Heater definitely working? Inspect all fish very closely including anus etc.
I find a tds meter quite handy.

 

[Country joe]

No I always double check I never miss dechlorinator I do add Easy Life which they say avoids antibiotics and Easy Life Catappa, and plant fertiliser and that's it,
I have inspected fish closely and they appear fine, maybe I will try 50% water changes. I don't know if treating for ich just in case, but don't think that would be a good idea.

 

[fish48]

yes do not treat fish unless really necessary , when a problem occurs s the first thing to do is a water change , ts annoying when you can't find the course of death in a fish, i keep a very large number of fish tanks and do a water change of 50% and very rarely have any problems

 

[Country joe]

I did a 25% waterchange on this tank on Sunday 20th April, should I do a 50% tomorrow?
Two weeks ago I changed my Fluval 307 on this tank to a Fluval 407, I changed all the media and sponges over, apart from the sponges that go down the side, as the 307 sponges were smaller, I tested the water every 2 days and all was good, could this have something to do with my problem,, would doing a 50% water change upset the bacteria in the tank. Sorry about all these different questions.

 

[fish48]

maybe that's the cause of problem. as long as you chlorinate the water a 50% water change shouldn't upset the bacteria

 

[WhistlingBadger]

Hm, I'm stumped. You've already eliminated all the usual suspects.
Straws to grasp at:
Is your heater working? (You said it's a constant temp but worth double checking)
Have you added any new decor, substrate, filter media, or anything else to your tank recently? Or is it possible that you have a piece of decor that is deteriorating and releasing something into the water?
Have you made any changes to your brand of dechlorinator or other water treatment?
Any changes in food lately?
Any possibility that something foreign (house plant leaves are a common culprit) is falling into your tank?

This kind of smells like a toxicity problem to me.

 

[WhistlingBadger]

Another thought: Is it possible that someone else in the house has been adding something to your tank without your knowledge?
(My college roommates added a bunch of tea bags to my goldfish tank once. Other than a bunch of highly energetic goldfish, no harm was done. But ever since then I'm a little paranoid)

The new fish might simply be bad stock. That doesn't explain your neon, but I'm seldom surprised when I have some losses in a new batch of fish.

 

[Country joe]

None of the above, when , I do my water change I put in 9 gallons, with 20 drops of prime added to my plastic bin, rightly or wrongly I've now added stability, and will do for seven days..then maybe I should change my water change to 50%
I had a word with one of the staff at my local store, not pah, she told me my nitrate should be nil, I explained I have a lot of plants, but said it should not be at nil, and my tank is not properly cycled.

 

[Innesfan]

Zero nitrate? I'm concerned the tank is not cycled.

Do you know which of the three rummynose species you have? Did you quarantine them? I have found H. bleheri, the most commonly available of the three species these days, often come in with health issues that can spread to other characins quickly.

 

[Country joe]

I don't know the species, I was going to quarantine them, but the manager whom I know, told me they had been in the shop for a month with no concerns

 

[Colin_T]

Need pictures and video of the fish.

Why did you change the filter media?
You only replace sponges if they start to fall apart and that doesn't normally happen until they are 10+ years old.

How long have you had the rummynose (a couple of days)?
If you have had the rummynose for less than 2 weeks, do not do any water changes for a couple of weeks, then only do 10% water changes once a week for a few weeks before increasing it to 20% for a few weeks.

Rummynose tetras have issues at certain times of the year and just drop dead for no reason. They show no signs of disease and just die. This is caused by either water chemistry changes or drug overdose. If the fish are wild caught they can be kept in really soft acidic water at the collectors (pH below 5.0 and a GH of 0ppm). If the suppliers have them in water with a higher pH they struggle and die. When the shops get them they usually end up in water with a higher pH again and the fish just die for no real reason. They will normally settle down after a month or so but you need to be very careful during this time because any sudden change can cause them to die.

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The drug overdose is from the suppliers and importers who treat the fish for everything because they are dying. They don't normally need treating and are dying because of a sudden rise in pH. The fish get weak from the chemical exposure and up and die for no apparent reason. Part of it is the fish's immune system is stuffed due to the chemicals and the fish can also become addicted to the chemicals and need them to live otherwise they go into shock and die.

The fish can survive the drug problems but they need to be kept really calm for at least a few weeks (preferably a month or more). This means low light and no water changes, and nobody going into the tank or stressing the fish in any way. We used to have the lights on but half to two thirds of the tank was covered with thin sheets of wood to stop any light getting into it. After a couple of weeks we allowed more light into the tank and over the next month we allowed more in.

You also need to turn the room lights on or open the curtains at least 30 (preferably 60) minutes before turning the tank lights on.

 

[anewbie]

Did you do a waterchange and had a sudden change in temperature when you did the change ?

 

[MaloK]

Media and filter replacement have already been discussed with @Country joe and as far as I know.

Has been done in the state of the art. All of the active bio-media where moved to the new filter box in addition new one was added and mechanical section was replaced. The lost active bacteria occupied surface was certainly very low, removing only the mechanical part.

I'm not really surprised with the 0 nitrate. bio-load is not heavy.

I'm inclined to think of something else. There must be.