Something odd with otto, something on its head?

Was contemplating my tank and noticed j couldn't find my 4th otto. These guys are masters of staying put and frozen, so after much search I found him sitting on a bambu leaf, and he seemed stuck. So, I moved the leaf and he moved away, but as he swam it seemed erratic, almost like he was just sinking and from time to time trying to right himself. A couple of times I saw him literally spinning around (vertically) before either allowing himself to sink to a plant or just the sand, or clamping to the glass for a bit before starting again.

He also looked discolored, very pale.

I just noticed him with better color, but there's this red thing on his head, and he's just looking "down" and lethargic

Can you tell anything from this image?

Nothing new in tank, and water parameters are as usual
Ph 6.5
Temp: 77-78 F
Water changed just yesterday (about 15%)
Zero ammonia
Zero nitrites
Nitrates 5 to 10

Tested using api master kit.

Any feedback would be appreciated


Tank mates are 4 cories, 14 neons (one was added about 3 weeks ago, a pity pick of a lonely neon at the local petco), 3 other ottos, and invader snails which have been on thr tank forever. tank has been running as it is for over 2 years.

As I was posting this, he got off the bottom and started the erratic swim again, video here:

Sorry, this isn't great news, but that guy probably doesn't have much hope.

I've had a couple of cories that have done the same thing and were told it was incurable once they start swimming like that. Has the same symptoms- clamped fins, pale, funky swimming. I think the cause, going from the replies I got to my posts on the same issue, is bacteria on the brain (or something like that...). Non-contagious, from what I can remember. It may be best to euthanize.

You could try adding salt (I did).

The red dot, however, I'm not sure. Pics don't really help, but could it be red blotch disease?

Sorry I can't be more helpful and hope it recovers.
PPJ

It has an infection in the brain. This is usually caused by protozoa but can also be caused by bacteria, virus or fungus. Normally tho it's from a protozoan infection. There's no cure so euthanise that fish and any that show those symptoms.

This normally occurs in dirty tanks or tanks with a lot of rotting matter. Do the following to reduce the chance of it spreading.

Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.

Do a 75% water change and gravel clean the substrate every day for a week. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.

Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.

Add some salt, (see directions below).

------------------------

The fish is also really skinny. This can be intestinal worms, gill flukes, or commonly with Otocinclus, starvation. They don't normally take dry food and need driftwood and algae. If you don't get much algae on the glass, increase the lighting period by an hour a day and see how it goes over 2 weeks. If there's still no algae on the glass, increase the light by another hour per day. Keep increasing the lighting until you get some green algae on the glass. You can have the lights on for up to 16 hours a day but you don't normally need that much to get a bit of algae growing.

You can also offer them cucumber, zucchini, pumpkin, etc, and some will graze on that.
Don't feed onions or onion relatives (spring onion, garlic, leek) and no potatoe.

If you ever buy Otocinclus catfish, make sure they have fat round bellies at the shop. Never buy skinny Otocinclus because they usually die.

------------------------

SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 2 heaped tablespoon per 20 litres (5 gallons) of water.

Keep the salt level like this for at least 2 weeks.

The salt will not affect the beneficial filter bacteria, fish, plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

When you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.

When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.

Well, he passed sometime last night. I did a good cleanup od this tank about 1 or 2 months ago (wiped the glass, cleaned the filters, yes, I have 2 filters running on it) the whole thing.
Just finished a 50% water change and filter media cleanup, and fished him out. The ammonia has not spiked despite his body sitting there all day, and thankfully, I suppose; he looked for a quiet cor er behind a rock for his final resting place, so nobody nibbled on his carcass.

I've tinkered wirh the light a bit to see if I can generate a better algae growth for the remaining ottos, although they've always looked good and busy grazing on the glass, the amazon sword leaves, the rocks, and the bambu leaves. They also eat the algae wafers I feed them.
I'm going to try zucchini again, I had stopped that last year because they didn't seem to care for it and it just sat there for a whole day without any fish really going for it. Probably will try spinach too.

If you used raw zucchini and they didn't like it, try sticking it in boiling water for 30-60 seconds. This can soften it up and some fish prefer it that way. Same deal with spinach, try some raw and some blanched (put in hot water to soften it).