Otto sick? Urgent!


Hello! First tank newbie here in dire need of assistance!! By the time this is posted it will be DIRE!!
I have an Otto in a 20gal tank that has been set up for about two months now, with the Otto being in the tank since around June 13th. He usually zips across the tank feeding all day on the algae growing on the plants or on the glass, though we haven’t been able to get him to eat the algae thins we had bought for him. He had been doing great, though the last two days he has been exhibiting strange hiding behaviour. We did not think much of it as he occasionally has a day or two which we don’t see him as often, but today we found him on the gravel of the tank, somewhat on his side and extremely lethargic. His breathing has already declined slightly and I believe he might be on his deathbed unless I manage to do something ASAP. I’ve done some research and looked through forums regarding similar topics but all of the cases I had read about the Otto was somewhat new to the tank. We did do about a 50% water change over the weekend, (I believe on Friday?) and changed two of our four cartridges in our filter the next day, and it had been a couple of days before his symptoms appeared. We have turned the lights in the tank off in hopes it might rejuvenate him? Help please!!! TIA!!!!

tank specs (from standard PH testing strip):
20 gal
Nitrate: 40
Nitrite: 0.5
pH: 7 (down from 7.5)
KH: 180
GH: 120
Ammonia (from standard testing strip): 0.5


Your tank isn’t cycled. You should be doing daily 50% WC’s till you can get the dangerous levels of ammonia and nitrites to zero. What size tank? Also when you clean your filter you should take a bucket of old tank water and swish around the cartridges to get the gunk off them and not replace them till their completely falling apart.
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**copied from the emergency questionnaire, answers underneath questions** thank you in advance for your help!!! <33
What is the water volume of the tank?
20 gal

How long has the tank been running?
Two months, fish have been in since ~June 13th

Does it have a filter?
Yes, a marina slim 20, 4 cartridge

Does it have a heater?
Yes, a 15-20 gallon auto heater from Walmart Canada

What is the water temperature?
24 Celsius or 76 Fahrenheit, though it was much warmer (about 78-80 Fahrenheit) with a heat wave which has ceased yesterday.

What is the entire stocking of this tank? (Please list all fish and inverts.)
1 Otto (subspecies not known, common is suspected, photos available at request!)
1 pleco (believed to be common, not albino or bristlenose)
3 adult silver lyretail molly, 3 fry silver lyretails
1 neon blue Mickey Mouse platy
2 neon tetras
1 random snail which was a stowaway and appeared in the tank one day, type unknown

How often do you change the water?
Every 1-2 weeks, has been less regular as our mollies just had fry and they would have been sucked up in our vacuum. The last water change was over the weekend on Friday? and 2 cartridges from the filter were replaced the day after.

How much of the water do you change?
25-50% depending on how dirty it is and the readings from our strips

What do you use to treat your water?
API water conditioner, API stresscoat and microbe-lift brand micro-blend. Not all at once and in accordance to directions

Do you vacuum the substrate or just the water?
Both the substrate and water, as well as decorations which collect large amounts of algae and detritus. The algae is left in adequate amounts to regenerate as the Otto does not eat the algae pucks which are placed in the tank

*Parameters - Very Important
Did you cycle your tank before adding fish?
Yes, we allowed the tank to cycle for 2-3 weeks, testing water parameters each day. Three plants were in the tank aiding the cycle as well as the liquid microbes we were adding as per regulations

What do you use to test the water?
API test strips, PH and Ammonia

What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0.5
Nitrite: 0.5
Nitrate: 40
pH: 7 (down from 7.5)

How often do you feed your fish?
3 times a day, once in the morning around 11am, in the afternoon between 3 and 4pm, and lastly at night at 10-11pm

How much do you feed your fish?
A pinch of two to three types of foods, depending on the time of feeding. Food usually lasts 3-7 minutes in the tank.

What brand of food do you feed your fish?
Tetramin tetra flakes, Fluval Bug Bites spirulina flakes, API Algae Eater wafers, Tetra freeze dried blood worms

Do you feed frozen or freeze-dried foods?
Only freeze dried blood worms as a snack

Illness & Symptoms
How long have you had this fish?
About a month, from ~June 13

How long ago did you first notice these symptoms?
About two days ago, when the Otto began exhibiting rather strange hiding behaviour. Our Otto normally zips across the tank feeding on algae, but has had a day or two of less activity before without concern.

In a few words, can you explain the symptoms?
Today, we had noticed the Otto laying on the gravel, slightly on its side, lethargic and with slightly laboured breathing which had declined in strength. We turned off the light and increased the strength in our air rock after reading that it may aid in lessening it’s stress. Since turning the light off about an hour ago, it has moved onto the front glass of the tank and has since disappeared, most likely hiding in a decoration.

Have you started any treatment for the illness?
No, as we are not sure what the illness may be.

Was your fish physically ill or injured upon
No, not that I am aware of.

How has its behavior and appearance changed, if at all?
For about 48 hours prior to issue the Otto began exhibiting rather strange hiding behaviour, no longer darting across the tank and sucking on the tank walls as it normally would. We were not initially concerned as he has had bouts of inactivity before, without cause for concern.
Once initially spotted on the gravel, the fins were held rather tight to the body, and the tail was moving less frequently. The mouth and gills of the Otto appeared to be moving adequately, but decreased in frequency and strength. After research we increased the strength of our air rocks and turned off the lights, causing the Otto to move onto the glass about an hour later, disappearing shortly after.

Explain your emergency situation in detail. (Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)
After about a 50% water change over the weekend, (I believe on Friday?), we had changed two of our four cartridges in our filter the next day. In hindsight after the water change he had began hiding, but that wasn’t entirely out of the ordinary. For the sake of readers I won’t repeat the limited symptoms again lol. Glad to see he is somewhat improving though, as I was certain he was on his deathbed.
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Your tank isn’t cycled. You should be doing daily 50% WC’s till you can get the dangerous levels of ammonia and nitrites to zero. What size tank? Also when you clean your filter you should take a bucket of old tank water and swish around the cartridges to get the gunk off them and not replace them till their completely falling apart.
I agree, and 20 gallon is a bit small.
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He’s moved twice, from the side of the glass and onto a suction cupped rock we have on the side of our tank now, so it is slightly promising that he has moved and is moving himself over. His tail still isn’t flicking about as it normally should though.

Darn it!!! Everything I’ve been told otherwise said it was cycled by June , we’ve had our fish for a month and not had any other problems aside from ich, which was given to our tank by adding a new fish without having a quarantine tank unfortunately, so I thought we were doing alright. We brought in a sample of our water to the aquarium shoppe before we bought them in May and the guy there tested it and said it was okay for fish . The tank had been set up for about a month with 3 live plants and liquid microbes before we added anything. We have had a spike in nitrates and ammonia though, they were normally much lower at around 0.5 nitrate and 0 nitrite since we were away for a weekend and came back to find small fry in the tank, and couldn’t fully change the water or vacuum the substrate for about half a week without killing them (they were so small!!). I also don’t know if their day caretaker has been adding their denitrifying bacteria when they should have been, which may explain the spike. Definitely my job now to say the least.

Lol yeah, 20 gal is pretty small, but where I live tanks are not super common or easy to get. We have been trying to upgrade to a 35 or 40 gal once we are able to get into the next province to go to PetSmart!

We have filter cartridges made up of small fibres, would they still be okay to use that long? I can take a picture to show what I mean )

Update: the Otto has now moved once again and his top fin is no longer as retracted to his body. I think the lights being off helps?

does anyone know if keeping the lights off will damage the rest of my fish?
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It looks like you may have accidentally put your tank through a mini cycle by changing the filter and doing a large water change at the same time, since your ammonia and nitrite are not at 0. (In a cycled tank, ammonia and nitrite should stay at 0).
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Thank you so much! That exactly explains it!! Others have been saying that we haven’t cycled our tank yet, but we know we had it set up properly before we added anyone to the water. Bad rookie mistake to make though

What would be the best way to ensure his survival? He’s moving around the tank a little more with the lights off and air rock turned up, but we’re not sure if the lack of lights are damaging anyone else or what really to do for the next step
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I agree that his "illness" is a reaction to the dramatic maintenance and, I think, possibly previous lack of maintenance (if that makes sense)
Feeding three times a day seems a bit excessive and then not changing water for up to two weeks with no gravel vacuuming is going to lead up to some pretty high levels of toxins in that water.
As I'm sure you know, otos are very sensitive to water quality and while the other fish will tolerate mini cycles/lack of maintenance, the oto cannot.
From your last post, it seems as though he might be turning a corner if the water parameters are improving.

Going forward, I'd suggest frequent small water changes (match the temperature really carefully and remove/add the water gently so as not to keep disturbing him) to try to control the toxins while the filter re-establishes.
As to not vacuuming due to having fry, they'll be fine! I have shrimp and am always vacuuming up the tiny babies, I just search for them in the bucket, net them and pop them back in the tank.
I'm not sure if having the light out is a good or bad thing, I'd think that as long as there's darker spots if he needs to hide, having them on won't be a problem (and the last thing that you want is for your plants to start dying off!)

And finally, if he does pull through, I'd like to recommend a couple of foods for him that mine love. The Repashy Supergreen and Soilent Green and Bacter ae by Glassgarten are all powders that I feed mine with. I just mix them up with a bit of tank water and shoot the mixture onto the leaves.

I hope that some of these suggestions help and that he pulls through, is there any improvement today?
All the best,
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