Sorry for the people that do not like a lot of reading. For the ones that maybe can use the lessons learned out of this I write it as complete as possible. Hopefully this allows also others to provide advice.
Status:
The TSN is doing better but still not as he should. I reckon that there was an “escalated start-up”. Stress and an irritated head. His head looks now quite well. No scratches. But I do think there are still some small pits to be seen. To my knowledge, this often takes some time to get rid of.
But in the basis I think there is still something not right. He is not as active as he should. He is not lying at the bottom but he is not swimming enough around. He is eating but sometimes it takes up to 10 minutes before he takes the food. Other times he takes it immediately. The time spam is too short to draw conclusions. But it looks like the better moments are having a relation to the water changes I do. So I reckon, I have to find out if this is true or not. Meaning I will focus mainly for a solution on monitoring the water quality closely and keep up a high rate of water exchanges. I had a high water change ratio when I figured out he was ill but reduced it when he was getting better.
Filter / feeding complication:
In addition to the above I discovered a complication with feeding / filter that possibly has effected the TSN.
I only have a relatively small closed filter. I bought it as a 2000 l/hr filter but it only does 1200 L/hr. It’s a Chinese pump and claiming the supplier is senseless. For a 500 liter tank 1200 L/hr is on the small side and considering the residents of the tank a more extended filtration would be highly desirable. But because the tank was only for the first two years and space is limited in my living room, I decided at start to only use an loose external filter. With my current knowledge I would have done it differently but I’m not going to change it anymore until building the next tank.
Today I added flow by using a “current\wave maker”. This to blow all dirt of the bottom into the water so the filter can pick it up. I noticed that there where fish particles coming from the bottom.
Afterwards I cleaned the filter. The filter was not as dirty as I expected but it did contain a lot of fish scales and small fish particles that had fungus on them! Never had this before. This can be caused by two (2) things that changed.
1) I have been feeding my caimans lately more. This because I have been examining their behavior under different feeding circumstances. A week ago I gave them fish. One of them was kind of “playing” with his fish before he swallowed it. Likely more loose parts of fish than normal ended up in the water.
2) The TSN is not directly eating his pieces of fish. I also feed him on a more regular base until he is 100% healthy again. So scales and small pieces can end up in the water.
The amount of particles with fungus where not enormous but possibly enough to have affect the health of the TSN. But it remains guessing what the impact could have been. Unfortunately I forgot to make pictures of the particles with fungus in the filter. The ones on the picture I picked out the water had coincidently(?) no fungus on them.
Water values:
The water values I measure hardly fluctuate. So quite identical to the ones earlier mentioned. In my rush I forgot to measure the water this morning before I started to work on the tank. I will measure the water tomorrow evening when I will again exchange some water.
Lycosid: I’m in the assumption that a NH4 of 0,05 mg/l is actually excellent for fish? According to the set NH4 up to 0,15 mg/l is acceptable and above 0,2 it is advised to change water. Is there something I’m missing/misunderstanding?
Sturgeon / catfish food:
After I had put some sturgeon pellets in the pieces of fish, which was eaten by him I tossed a lose piece of sturgeon food into the water. It took it straight away with big force! I was really surprised. So I tossed a Tetra Cichlid pellet in. He checked it out but never took it. Then I tossed another sturgeon pellet into the tank. He took it again straight away. He clearly like the smelly sturgeon food with a crude fat that is way too high.
So I bought a bag of sturgeon pellets at a shop with a lot of knowledge of cold water pond fish. They also have their own brand of fish food and supply 1,5 kg sturgeon food for 7,45 Euro that has a crude fat percentage of 12%. So in the lower range for sturgeon but too high for a TSN.
I asked why the amount of fat was so high in sturgeon food in comparison to fish food for catfish while their natural food sources do not much differ. He said it is exactly the same food. I can order the exact same pellets in a catfish bag! He explained that sturgeons always have to keep swimming and due to that burn a lot of energy. If a food for sturgeon is used with a low crude fat percentage you either have to feed them a lot more which results in more water pollution or they will starve. I reckon the latest is probably a bit exaggerated but I guess I understand what he was trying to say. The reason he is selling sturgeon food with a lower fat percentage (12%) in contrary to a more normal figure of 17%-22% was that koi will always eat some sturgeon food as well if they share a pond and this makes it just a little less bad for the koi. People often feed their fish more than they should. So the 12% works from a practical point of view well.
Why the 12% crude fat food for sturgeon was identical as for
coldwater catfish was that you should not feed them that often in comparison to sturgeon and the 12% is also a balance between winter and summer time. I‘m still digesting this latest part of the answer myself. I would reckon that if temperatures get lower European catfish lower their activity and their metabolism. But maybe this is not the case or not for the pre winter / autumn and pre summer/spring periods. Anyway he mentioned that beside the crude fat percentage the analyses was perfect also for tropical catfish. He emphasized not to use koi food that has the right amount of crude fat of 3%-5% but an analyses that differs significantly.
At home I noticed that his food smelled more like dog food then the sturgeon pellets I had from the other store. The other ones had a more particular and stronger smell but the negative 17% crude fat. The new pellets I have are 6mm in diameter. The last days he didn’t eat that well so I have to wait till he is eating well again to test these pellets. They sink and I do not have other fish to clean the food up if he doesn’t eat it.
Note: I will only use these pellets as an addition to fish and “large shrimps” and not his main source of food!
The gamba bag was empty so I bought this time a box of two (2) kg of large shrimps, raw, unpeeled and even with head. See picture. It cost me 28 Euro’s. They are size 6-8.
Unfortunately the TSN was continuously hiding today so No “recent” picture. But as soon as he is out in the open I will make one. The one below was made earlier this week!