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I have a sick pimelodus pictus - anyone help IDing the illness...

Only noticed problem today. Floating up near top of tank, unable to balance/keep upright, swollen around head area, barbels are missing, some red/bloody area around fin on top of it's body. All other inhabitants in the tank seem fine inlcuding the 3 other pim pics.

Water chem Ph 6.5, No nitrites, 160 nitrates, no ammonia, Temp 25 celcius.

No sudden changes etc. Have moved sick fellow to quarantine and really don't think he'll make it. Will do water change on main tank to get rid of those nitrates. Normally do 30% change 4 weekly which has worked really well. Tank is overdue by about 1 week for change of water.

160 ppm nitrate? That is quite possibly part of the problem. These fish are really not good with high levels of nitrate, and anything over 50 ppm counts as "high".

If your nitrates are 160 ppm after 5 weeks of no water change, you really, _REALLY_ need to change water more often. I change water once a week (give or take a day) on all tanks except the ones that are "automatic" water changes.

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Mats

Normally the nitrates sit about 20 (just before the water change) so I guess something has changed to cause the sudden jump.

Chemma,
Just some friendly advice with regard to river Pims. Fishes that in habit the main sections of rivers (like P. pictus) are especially bothered by poor water conditions as they are rarely exposed to large fluctuations. Fishes found in swamps, pools, and other small water bodies tend to be far more tolerant of unfavorable water conditions.
To have long term success you will really need to get the tank on a schedule of frequent large water changes. I would not keep even swamp fishes in a lightly stocked, heavily planted tank on a schedule of a 30% water change once a month. With Pims like these you should be shooting for a change of 60-70 percent weekly.
-Shane

Shane wrote:With Pims like these you should be shooting for a change of 60-70 percent weekly.

And to make sure there aren't huge fluctuations, I'd recommend spreading that over two water changes of 30-35% each time.

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Mats

And to make sure there aren't huge fluctuations, I'd recommend spreading that over two water changes of 30-35% each time.

I think Mats means in the beginning as you stabilize your tank to clean water?

Fluctuations in water chemistry are far smaller with frequent, high volume water changes than infrequent, small volume ones. Once you are on a schedule of large water changes the tank will reach complete stability as it will be kept in a state of constant fresh and clean water. The pH will never have a chance to decrease, nitrates and nitrites will never have a chance to build up, rotting food will not impact the tank's chemistry, etc, etc as all these pollutants will be removed constantly.

I read an interesting article once that I wish I had kept close at hand. It showed the compound impact of small, infrequent water changes over time. Imagine this situation. The tank's residents raise the nitrates by 10 ppm per week. The aquarist changes 30% of the tank's volume per month.
Week 1: Nitrates 10 ppm
Week 2: 20 ppm
Week 3: 30 ppm
Week 4: 40 ppm
30% water change, nitrates lowered to 28 ppm (lowered by 30%)
Week 5: 38 ppm (note, 1 week after our water change, the tank is as "dirty" as it was before!)
Week 6: 48 ppm
Week 7: 58 ppm
Week 8: 68 ppm
30% water change, nitrates lowered to 47.6 ppm (lowered by 30%)

As you can see, this is a never winning battle. Filtration will slow this process (i.e. it will reduce the 10 ppm produced daily by a percentage depending on how good the filter(s) are), but it can not halt the degredation to water quality noted above forever.

My entire fishroom gets a 70-80% water change every Saturday. For most aquarists, once you have all the kit out it is just as easy to do more than less.
-Shane

I would make 2 remarks for the above

1 filtration does not reduce nitrates in the water. biologic filtration normally enhances the production of nitrate (less toxic then ammonia / nitrite which are more abundnet in the water without filtration) while megenic filtration remouves stuff before it can release any ammonia/ nitrite or nitrates from the water

2 if the production of nitrate is 10 ppm a week and 30 % of the watrer is filtered monthly, than after a while the nitrate content of the water will be high enough that this 30 % of water takes the whole month-production with it - that is the 40 ppm. However, this is only met at a nitrate concentration of 130 ppm - and after changing water 90 ppm. In other words, and that is what Shane inplied, I think, water which is toxic to many fishes

Were the nitrate production half the given value, the equilibrium would be reached at half the nitrate in the tank - still a lot, but for some fish acceptable

Therefore, a given fish might be able to survive in a twice as large tank, or you better change water more often.

What I actually meant is that if you do two smaller changes, the levels of nitrate and other waste products varies less, and the overall level would be lower.

But I also agree that it's not a good plan to make large water changes on tank that has "old" water, as it can shock the fish. It's almost always OK, but not guaranteed.

I do large water changes once a week on some of my tanks - most of my tanks get automatic water changes. The tanks that use the waste-water from the RO system has a continuous flow of "fresh" water that means the entire volume of the system gets replaced around 5 times each week.

--
Mats

Thanks Gang, consider lesson learnt

chemma wrote:Thanks Gang, consider lesson learnt

Understood, but I feel, like Bas, that it is better to begin with a much larger water change. 50% minimum but I use 70% normally. When it comes to nitrate reduction from high levels it is best to make those water changes large and more frequently until you resolve the high nitrate conditions. As long as the replacement water is prepared in advance to match the pH and hardness then large water changes are not a problem. ( so says a Discus breeder with more than 4 decades of experience). I simply add SeaChem Prime, my preferred Chlorine/Chloramine neutralizer to the aquarium then refill directly from a faucet after adjusting for temperature. Even Discus have no problems using this method.
As to the afflicted Pimelodus pictus, I doubt it will be saved if it hasn't died already. I like to include a power head in their tank because they enjoy brisk currents.