Corydoras sick again

Apparently I screwed up again somewhere.
One of my corydoras is sick, it is way whiter than the others, less active. I noticed only today, didnt think it has been in this state long.
I suspect something happened in the tank and since I now see only 3 otocinclus, not 4, I guess a dead fish is there somewhere.

Last clean of the tank was 4 days ago, 30% water change and the pre-filter sponge was thoroughly washed. The tank is now super filled with plants and green hair algae, but I assumed the naias explosion would have reduced potential issues. I was wrong. I didnt do substrate clean in this WC, because I needed cleaner/ish water to wash the sponge in (I dont wash it in tap water, increasing the space for bacteria, so I have 30x10x10 sponge and large eheim 2217 with 4 sponges and eheim substrate balls or what is it called). Last filter clean was 2 months ago.

From other topic I have opened here I understand I wasnt feeding it that well, since the wafers I used were not good, so the fishes dont have the best immune system. I am going to do a gravel clean 50% WC today and filter clean on sunday or monday (I am ofcourse leaving today, returning not sure when on sunday, since I am going to be working tomorrow from 6 am wake up to 4 am end of the party I am catering, catch some sleep and then have to load all and drive 3 hours back. Best timing as always)

Is it worth also catching the cory today and giving it a targeted salt bath for 15 minutes? Does the corydoras even have a chance to survive this? It really doesnt look good, though at least it has barbels. Moving it is out of question.
Thanks

The others look ok, they are around a year old, I havent added anything new any time in the past few weeks, no changes.

What exactly are they fed.
Why a saltbath exactly ?

Once every 10 or so days I feed half a cube of frozen bloodworms specifically for the corydoras (though I started this like 2 weeks ago). Once a week I feed half a cube of frozen daphnia and cyclops, usually space at least a day between the frozen food. At the days I dont feed the frozen cube, I will drop 2 wafers, either protein content (35% of protein but the wrong kind, fish bits, starch,...), or spirulina content, I switch them. At these days I also at a different interval either use hikari micro pellets or sera vipan baby or lyophilized artemia. Once a week in the summer I fed live mosquito larva, but they are not available at this moment. Also once every 4 days or so I drop in a blanched vegetable. I dont feed at all on at least a day or will do a morning feeding and the next day an evening feeding

And salt bath might help if it were fungus or bacteria...it seems a bit slimy to me

Beastije said:

Once every 10 or so days I feed half a cube of frozen bloodworms specifically for the corydoras (though I started this like 2 weeks ago). Once a week I feed half a cube of frozen daphnia and cyclops, usually space at least a day between the frozen food. At the days I dont feed the frozen cube, I will drop 2 wafers, either protein content (35% of protein but the wrong kind, fish bits, starch,...), or spirulina content, I switch them. At these days I also at a different interval either use hikari micro pellets or sera vipan baby or lyophilized artemia. Once a week in the summer I fed live mosquito larva, but they are not available at this moment. Also once every 4 days or so I drop in a blanched vegetable. I dont feed at all on at least a day or will do a morning feeding and the next day an evening feeding

And salt bath might help if it were fungus or bacteria...it seems a bit slimy to me

Click to expand...

I think it is an internal issue instead of an external one and maybe the slimecoat reacts to that. The fish's shape doesn't look right (thin).

The diet doesn't seem the issue.

So, what shall I do?

Are you showing any ammonia, nitrites or nitrates?

#1 thing to do with a sick fish is eliminate any extra stress, and ammonia, nitrites and nitrates could be causing stress, especially considering you cleaned the filter, maybe harmed some of the bacteria?

I think I would forego doing any filter cleanings right now, but the gravel vac/water change is a good idea.

I tested from the surface area, 0 on the NO2, will test from a bottom area sample before I go do the gravel clean.

I would not subject the fish to a salt bath which will without question add more stress (the netting and the salt bath), and there is no reason visible for this. I would however do water changes, 70% provided parameters (GH, pH and temperature) of tap and tank water are the same (reasonably).

The dead oto (if it is) would not do this or anything else here, the plants easily handle any ammonia. We've discussed the foods in the other thread and I agree they alone are not responsible for this, but changing the diet as discussed there will help the cories.

Water parameters didn't change. I did a drop test, kH is 2 dkh, gh is 6dkh same as in the spring. Oh is around 7,4 maybe higher they only sell test here till 7,4

Tap water according to vendor has 7,9 but i doubt it. Other params are same in tap and tank water from the tests i have.

I did a 50% change, increased flow and pointed it to the middle of the tank

Either my ph is too high for the fish or the sand is perhaps wrong I was thinking about replacing it. It used to be pool filtration sand when I bought it 10 years ago but i did add new layer of it last year or so. Still very strange
I guess will hope for the best for Sunday

Don't be shy about cleaning the filter or the substrate (or indeed doing water changes). This is an established tank so the beneficial bacteria will be robust. Once a tank is established for a year, the filter sponge can be rinsed under a tap.
I'm sure Doubledutch is correct about an internal issue. With any disease pathogens can be reduced with regular large water changes, substrate cleans and filter cleaning.

We are all in agreement, I think. Food is not the direct issue but changing the diet will benefit the cories regardless. The plants will deal with any ammonia/nitrite so these should remain zero. Fish do get sick, it could be genetic, pathogen, injury... . So long as it does not show signs of spreading, I would just leave it. Stressing all the fish by using treatments that likely won't do anything positive is only going to risk all of them.

Damn the fish just died. Two days since noticing symptoms and death despite water change.
Damn i am worried.

Anyways, what can I change now to avoid this in the future?
I purchased 15 in October last year, and I have only 10 of them now. Sure, the food is a problem

I will change the diet first and what, wait two three months to see any changes, like them growing up and being fuller?
Or do I also change the sand for a more suitable one, in case this is the issue, as I understand PFS is not good for them at all.

Today or tomorrow I will clean the filter anyways and do another water change. Apart of losing this corydoras, I also lost almost all of the otocinclus. Granted I only have had them for 3,5 months, but out of 10 I had I now only have 3?! I assume the spirulina tablet is also not good, but damn they eat everything I put in there, I have blanched vegetables, greens, soaked leaves with slime coat
What has happened, could it be the source of the fish, maybe they were older (I lost trust in the seller, who knows where and how he got them)? I have so much algae and I assumed all was going well, they had round bellies and were real good. I wonder if I should get another batch from different seller and try again, or if I should just give up.
I read all about repashy and home made otocinclus foods and spirulinas and I ordered also better spirulina wafers. But I am so sad now

As already stated, the direct cause of the death(s) can be one of several things. The diet is the one thing I would correct because this will provide more of what the fish need, and that should result in healthier fish.