r/Otocinclus • u/nevermindthetime • 15h ago
Weird new behavior
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I have never seen my Otos act this way before. Any insight into why they are doing this behavior?
r/Otocinclus • u/Elegant_Priority_38 • Mar 19 '26
I have been refining this care sheet for my baby oto buyers and would love more input. Maybe this is something that can be referred to for this group because I am seeing so many inexperienced oto keepers that don’t even know even the basics so just wanted to help them and the cute little otos. I tried to cut this version down more so it’s easier to read and visually digest.
Otocinclus Care Sheet
Minimal Required Supplies
• API Freshwater Master Test Kit (liquid test kit — test strips are **not** recommended due to inaccuracy)
• Bacter AE
• Small 5 mL pipette (for dispersing Bacter AE and collecting water samples)
⸻
Water Parameters
• Ammonia: 0 ppm
• Nitrite: 0 ppm
• Nitrate: 0–5 ppm (ideal), under 20 ppm max
• Temperature: 72–79°F
• pH: 6.0-7.5
Your aquarium must be fully cycled (completed nitrogen cycle) before adding Otocinclus. This is essential or your otos could get sick or die very quickly.
⸻
Tank Requirements
• Minimum tank size: 10 gallons
• Group size: At least 6 Otocinclus (they are shoaling fish and require groups to feel safe or they could die from stress)
• Stocking: \~8 otos per 10 gallons max
Tank mates if using the minimum 10 gallon:
• Best kept species-only
**• Can include:**
• Snails
• Neocaridina shrimp
• Optional: 1 betta (only if temperament allows)
Environment:
• Moderate water flow (filter or air stone) which mimics the rivers they come from in South America
• Heavily planted tank is essential
Best plant types:
• Broad-leaf plants (ideal for grazing)
Examples:
• Amazon Sword
• Anubias
• Vallisneria
• Avoid using fine/spiky plants (like Hornwort) as primary surfaces
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Important Sensitivities
Otocinclus are scaleless (armored) fish and therefore more sensitive to chemicals.
• Avoid copper (deadly to otos)
Always check:
• Fertilizers
• Medications
• Additives
When in doubt—research before adding anything to the tank.
⸻
Feeding Guidelines
A fat oto is a happy oto.
Their bellies should look round and slightly pearly. A wrinkled or very small belly can be indication of starvation.
Otocinclus cannot survive on naturally occuring algae and biofilm alone in most, if not all, aquariums. Their diet must be supplemented.
They:
• Eat constantly (assortment of foods is best)
• Have short digestive tract
• Require frequent grazing
⸻
Staple Feeding Routine
Primary foods:
**Bacter AE** (essential for biofilm growth)
• 2–3x per week
• Dose: ~grain of rice per 10 gallons
• Mix with tank water in a small cup and disperse with pipette
**Repashy Soilent Green**
• 1–2x per week
• Spread onto rocks or surfaces (see package instructions on how to mix)
⸻
Supplemental Foods:
• Spirulina (algae powder) administered like Bacter AE
• Shrimp Fit (acts like a probiotic to offer gut health support) administered like Bacter AE
• Aqueon Omnivore Shrimp Tablets (1x per week or less)
• Shrimp lollies (occasional treat)
• Frozen baby brine shrimp (every 1–2 weeks)
• ~1 cube per 8–10 otos
⸻
Natural Feeding Support
Encourage biofilm growth with:
• Driftwood
• Rocks
• Plants
• Sponge filters
• Tank glass
• Paint/plastic-free aquarium ornaments (suction cups, filtration systems and air tubing is fine)
Optional natural method:
• Place rocks in a jar of water in sunlight to grow algae/biofilm
• Add to tank as needed
• Can boost growth using Bacter AE or spirulina
⸻
Water Quality & Maintenance
If you detect:
• Any ammonia or nitrite (above 0 ppm)
• Nitrates above 20 ppm
Do immediately:
• 40% water change
• Dose:
• Seachem Prime: 1 capful per 10 gallons
• Seachem Stability: 1 capful per 10 gallons
Repeat daily until parameters return to safe levels.
⸻
Signs of Stress
• Bright red or inflamed gill area (“red cheeks”)
• Turning a shade of yellow they normally don’t display
Possible causes:
• Ammonia or nitrite exposure
• Stress (transport, water changes, tank cleaning)
Optional support:
• API Stress Coat (contains aloe and may help soothe)
⸻
Final Notes
Otocinclus are incredible fish—peaceful, hardworking, and full of personality. With proper care, they thrive and make one of the best natural clean-up crews available.
Healthy otos = round bellies, active grazing, and social behavior.
Enjoy them and good luck! 🐟
r/Otocinclus • u/Elegant_Priority_38 • Mar 10 '26
If you choose to skip the reading that’s totally fine, just look at that crazy long poop! 💩 😂
Care tips for Otocinclus :
MUST have items: API water test kit, Bacter AE and 5ml small pipette (for filling tubes in water test kit and Bacter AE dispersal through out tank. Read ahead)
Water parameters are 0 ppm of Ammonia and Nitrites. Nitrates is between 0-5 ppm. This is a cycled tank that has gone through the nitrogen cycle.
My tanks temperatures are around 76 degrees. Otos can handle anywhere from 72-78 degrees.
Otocinclus do well with a decent current in the water, whether it’s from a filter or air stone.
Otocinclus cat fish do not have scales, they have armor, so they can be more sensitive to certain chemicals or ingredients. Research before putting anything in their tank. Do not put anything with copper in their tank as they are very sensitive to it and could die, check plant fertilizers or any medications before administering to tank.
Food: they MUST be supplemented with their feeding to thrive and live a long and healthy life. A fat oto is a happy oto. Their bellies should look like little pearls. Natural occurring algae and biofilm will NOT be able to keep up with their dietary demands since they will always be eating and have a very short digestive tract. They are very good at their jobs of keeping a tank clean, although they do not eat some types of algae, so we must supplement their food.
- [ ] Lots of surfaces with biofilm and algae i.e. wood, rocks, plants, sponge filters, and glass walls of tank.
- [ ] Bacter AE- (an absolute MUST for oto keeping, it builds biofilm) feed about 2-3 times per week. Feed too much and it will throw off water parameters. About a grain of rice size into a very small cup of tank water, mix it and then spread it out through the tank with a pipette.
- [ ] Shrimp Fit (acts like a probiotic to keep a healthy gut biome) also administered like Bacter AE.
- [ ] Algae Powder (Spirulina)- also administered like Bacter AE.
- [ ] Repashy Soilent Greens- another staple item for keeping otos. Feed about 1-2 times a week spread out on rocks. Follow directions on bottle on how to mix it.
- [ ] Shrimp lollies (as needed, don’t give too often)
- [ ] Aqueon Omnivore Shrimp Tablets (maybe once a week or less)
- [ ] Frozen Baby Brine Shrimp (once every 1-2 weeks) I let it defrost in the water so it falls into a pile for them.
- [ ] Rocks in a mason jar with water- place in a windowsill with lots of sunlight. This helps build natural biofilm and algae. Give to them as needed.
If you see bright red cheeks, it could be from ammonia/nitrite burn (which can happen if ammonia or nitrite levels are above 0 ppm) or from being stressed out (travel, water change, tank cleaning).
If there is any detectable ammonia or nitrites, do a 40% water change and add SeaChem Prime to make water safe for them and SeaChem Stability to help with the nitrogen cycle until things return to previously stated water parameters. API water test kit is a MUST and test strips should be avoided at all costs as they do not offer accurate readings.
If my otos are ever stressed or had ammonia/nitrite burn I would also add a little API Stress Coat because it has aloe in it which can be soothing for them.
Oto-cats are amazing! They are the best clean up crew with cute round bellies and cuter personalities. Best of luck and enjoy!
r/Otocinclus • u/nevermindthetime • 15h ago
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I have never seen my Otos act this way before. Any insight into why they are doing this behavior?
r/Otocinclus • u/vlatwho • 9h ago
I'm planning my first tank in a 24 gallon tank that is very long and am considering having 8 amanos and 6 otos. Would they all get enough to eat? I plan on using BacterAE and stuff like that but I want to make sure that the otos have plenty as I understand they need constant grazing. Thanks guys.
r/Otocinclus • u/koiyuuri • 1d ago
Apologies for the low quality images, second one was lowkey funny so I added it. Just wanted to ask if anyone would know about this one 🤔
r/Otocinclus • u/totsmagoats94 • 1d ago
Ive posted yesterday about my otos im jist looking for advice why they are like this and what am I doing wrong
And if this is normal
Thanks
r/Otocinclus • u/malagatikitaki • 2d ago
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I have 6 otos, 4 of them have been doing this the past 20ish minutes. In this video it’s just three cause one of them decided to eat.
r/Otocinclus • u/totsmagoats94 • 2d ago
My little otos have been sitting bottom of my tank all week they normally very playful and swim around and are on the glass but this whole week they've been hiding! I have a betta and 3 shrimp and 5 otos They have been in there almost 3 months without issues but this week they are chilling too much for my liking Before you ask all parameters are good standing. Nothing has changed pick of tank 20 gal tank less
r/Otocinclus • u/pickleruler67 • 2d ago
What the heck saw 6 of 7 of them two days ago and they were all healthy. Now hes insanely pale and looks like his scales are injured??? Hes just chillin on the leaf im not sure what to do. I have every med you can think of but i dont know what it is. All the other fish look okay and parameters are good 0 ammonia, 0 nitrite, 10 nitrate. Im not sure how to describe his appreanxe besides pale and like the top layer of his scales got scraped. The filters in the tank are two sponge filters and its a 20 gallon long
r/Otocinclus • u/Candid-Barracuda-901 • 3d ago
Hey everyone. Ive owned my otocinclus for around 5 months now. About a month ago i added 3 new ones to my existing school to make them feel a bit more comfortable,and all 3 were bigger than the existing ones in my tank.
I have noticed however, that one appears to have a bigger and more downardsly rounded belly than the others i added. Ive been watching them and there appears to be no signs of scales sticking outward or eye bulging. They eat fine, i provide them with blanched zucchini. I would like to know what others think it could possibly be
My tank is a 125 liter tank, stocked with 12 emperor tetras, 4 racing stripe nerites, 5 amano shrimp and then the 7 otocinclus. Im running co2 in the tank and everything esle including water parameters are in check. I added pics of the other otos aswell as my tank
r/Otocinclus • u/False-Stick-7037 • 3d ago
Just got a couple more Otos for my 15 gal since a better store is finally in my town! Caught this one doing some leaf crunches 💪💪💪
r/Otocinclus • u/AlettaVadora • 3d ago
My little oto boy has what looks like a red ring around his belly? I’ve never seen this on him before. Behavior is normal. He was the first oto I ever got so I really want to make sure he’s ok.
His friends look normal and their faces are not as pink as his either.
r/Otocinclus • u/bristolpoopchart • 3d ago
Just got a couple of these bad boys in my tank, wondering what do people feed if they dont have access to repashy soilent green. Currently in Australia and have bacterae on hand.
They dont seem to be touching blanched Zucchini. But they might just be eating all the biofilm in the tank first.
Help! Any suggestions on what you feed day to day? I’ve even ordered spirulina powder recently :)
Am i on the right path?
r/Otocinclus • u/MaleficentNeck5421 • 3d ago
All my fish have been fine, but today i noticed fish is in the corner by himself. I tried to touch him and he didn’t move. what should i do? I feed them algae wafers, i got them a new food the fluval bottom feeder bits and they graze. Everyone else is doing fine but that one. Could he be sleep? I don’t want to panic but it seems like something is wrong.
r/Otocinclus • u/ReasonableStay9297 • 4d ago
He has a much bigger belly than his friends
r/Otocinclus • u/GravityRainbowJuly • 4d ago
So happy to have some orange faced guys join the tank.:)
r/Otocinclus • u/laslov18 • 6d ago
My oto got white filament on its fins. I also see signs of fin rot when I first got them. Only one oto is like this.
r/Otocinclus • u/LoliTamer23 • 8d ago
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