Some Corydoras Trilineatus Trouble. Due To Water Parameters?

[EddyBearr]

So, I have an aquarium with 5 Corydoras Trilineatus. I've had them for maybe 8 months now, and I think I can safely say that they're some very hardy ones.
 

Here are some bullet points for all information I think is relevant.
 
Tank:
-30 gallons (3'H x 1'W x 18"H)
-Play sand substrate
--Malaysian burrowing snails made the surface of the substrate gravel, with sand underneath. Thinking of removing larger pebbles from sand, or putting new sand in.
-Recent algae/plant die-off
-Water parameters should be a little uncomfortable for the corydoras
 
Corydoras:
-Behavior is mostly normal. They eat, they rest, they scavenge, and they play
-Occasionally scratching themselves on the gravel, usually on the side
-Barbels on 2/5 are worn, barbels on 1 are gone. 2 are just fine
-Resting at 30°-80° angles on the gravel (the ones with injured barbels) Illustration: http/i.imgur.com/CbLsLkh.png
-the 2/5 with worn barbels are female. Other 3 are male.
-1 Female has been plump for a while. The other was somewhat thin from having laid but has plumped up a lot this last week (this is due to feeding less attempting to kill off algae & postpone egg-laying. It worked. I've returned to feeding them well.)
-Plumpest female occasionally clamps (very loosely) her dorsal fin 
 
 
Water parameters: 
PH: ~8.0
Ammonia: ~0.25 ppm
Nitrite: ~0.1 ppm
Nitrate: ~8 ppm

Temperature: Trying to keep it at 72ºF, but has dropped regularly to 64ºF at times due to weather. I wish I could get it to 75º-78ºF and stabilize it, but I think it needs a different heater.
 
No clue what the KH is, but I don't have any reason to think it's terribly abnormal.
 
The likeliness of the corydoras scratching due to parasites is very slim. No other signs, no problems with other fish, and it's been going on for a few weeks.
 
Would I be correct to assume that the abnormal behavior is the result of the water parameters? Should I make the surface sandier again? Their barbels were fine until a couple weeks ago. The sand sifted down months ago. If the parameters are set straight, will the corydoras stop scratching and resting abnormally? I'm thinking the barbels being cut is a result of them scratching due to parameter issues.

About to do a decent sized water change, including some RO water, to bring PH down and get ammonia/nitrite down. Recently lost a lot of my beneficial bacteria due to scrubbing my bogwood to kill Black Brush Algae, and had a spike due to plants & algae dying.

 

[eaglesaquarium]

There are a few items that stand out to me:
 
 

• Lack of barbels
• scratching on gravel
• pH
• ammonia/nitrite

 
 
The pH for cories is best in the range of 6.0-7.0.  You can keep them at higher pH, but it isn't recommended.
 
The lack of barbels is probably due to infections caused by a dirty tank.  Even in a tank with gravel, they won't have worn barbels unless the water quality is low and/or the gravel is extremely sharp.
 
The scratching on the side is the most peculiar.  This could indicate a parasite of some sort, possibly in the gills.
 
And obviously, the ammonia and nitrite is an issue.  I think the issue with that is from the plant die off, not from scrubbing the driftwood.  Most of the bacteria leave in the filter, plus the rest live on all other surfaces.  Scrubbing one won't have a huge impact on the colony, and the rest of the colony could reproduce to more than make up for what might have been lost.

 

[EddyBearr]

There are a few items that stand out to me:
 
 

• Lack of barbels
• scratching on gravel
• pH
• ammonia/nitrite

 
 
The pH for cories is best in the range of 6.0-7.0.  You can keep them at higher pH, but it isn't recommended.
 
The lack of barbels is probably due to infections caused by a dirty tank.  Even in a tank with gravel, they won't have worn barbels unless the water quality is low and/or the gravel is extremely sharp.
 
The scratching on the side is the most peculiar.  This could indicate a parasite of some sort, possibly in the gills.

 
Yeah, I did about an 8 gallon water change (5 gallons RO water, 3 gallons tap water.) Tap water PH is about 7.4, and I know that RO water will bring the PH down. I'll follow it up with another 5 gallon water change, or so, perhaps Thursday morning, and test the water parameters again thursday afternoon. (GMT -6)

I went through with the water change, and scrubbed a lot of algae off the glass as well, just for aesthetic reasons. Unfortunately, I found out some more about the corydoras. My small male who is basically completely without barbels seems to have swim bladder issue. The resting at weird angles seems to be a result of swim bladder issues.

As noted, my less-plump female has really gained weight this last 2 weeks, as I have been feeding pretty heavily, so for now I'm hoping it's constipation. I don't think it's red blotch disease, because while there is a little redness in some of the fish, I think it has more to do with basic stress from water conditions and swimming troubles. Interestingly, the larger the corydoras get, the less likely they were to have symptoms, which further suggests it's from overfeeding.

I've fed them peas and am now going to fast them until Thursday, including the guppy tankmates (the guppies will help eat up whats left of algae, hopefully. They're definitely algae eating fiends.)

Interestingly, they do seem slightly better already. The two large corydoras were never a trouble, the two female corydoras seem to be slightly better in the sense that they aren't resting at weird angles, and the small male corydora, who was having the most trouble, isn't doing as poorly as he was last night, and now he's actually hanging out with the crowd again (we noticed he was isolating himself.)

Man, these cories are tough! Missing barbels, (presumably) constipated, and bad water conditions, all at the same time.

We'll see if the flashing stops, which I've read can be caused by unfavorable water conditions irritating the corydoras relatively delicate skin, and hopefully the swim-bladder-problem-esque symptoms disappear as well. The barbels will be another story..

 

[eaglesaquarium]

The problem with RO water is that it isn't going to really do much long-term for the pH.
 
 
Why does the pH rise in the tank compared to the tap?  Did you test the tap pH straight away or after it sits for 24 hours?  Letting it sit will allow gases (like CO2) which can acidify the water escape, meaning the pH can rise after being added to the tank.  If that's not the root cause, then something in the tank must be leaching into the water increasing the pH. 
 
 
What's the hardness of your water?  Cories also prefer soft water.

 

[EddyBearr]

The problem with RO water is that it isn't going to really do much long-term for the pH.
 
 
Why does the pH rise in the tank compared to the tap?  Did you test the tap pH straight away or after it sits for 24 hours?  Letting it sit will allow gases (like CO2) which can acidify the water escape, meaning the pH can rise after being added to the tank.  If that's not the root cause, then something in the tank must be leaching into the water increasing the pH. 
 
 
What's the hardness of your water?  Cories also prefer soft water.

That's tested right out of the faucet. I have some tap water that's been running in a bucket with an empty filter (to clean the filter) for about a week, and it's PH is about 7.8. 

I have no clue what the KH is, and my city doesn't record that information. I couldn't find a KH tester at a store either (though admittedly I didn't look that hard.)

The algae has been bothering me, and I'm thinking it might be due to too much light for the amount of CO2 I have. I have a T5 light fixture. I'm starting to think that getting some CO2 in the tank would help, or perhaps weakening the surface current (which I'm trying to weaken by growing some floating plants.) More CO2 might help both the PH and the plants.

I believe my filter works for 30-50 gallons. T5 light fixture. Enough plants to stuff into perhaps a 3 liter bucket (would be pretty stuffed.)

A large amount of snails, the 5 corydoras, 6 guppies (4 medium sized females and 2 small endler males,) and a middle-aged betta.

 

[DoubleDutch]

What do you feed your Corys? Did you clean your filter recently and how do you do that? Greetz aad

 

[EddyBearr]

What do you feed your Corys? Did you clean your filter recently and how do you do that? Greetz aad

I feed them Hikari sinking wafers (spirulina, silkworm, krill) they also eat some pretty quality flake food at times, and once in a blue moon they'll steal the betta's pellets if he misses them.

I was definitely overfeeding them.

Filter hasn't been messed with in months. It's well-established at this point. The filter I was cleaning was an extra filter I want to use in another tank.

 

[snazy]

The issue is your ammonia and nitrIte reading. My corys will scratch themselves even if the test shows undetectable and that's when I overclean the filters.
You need to do larger water changes when you've got a reading. A 5G water change will remove just 23% of the detected ammonia/nitrIte. Do adequate water changes to remove all of it at once.
All the other cory issues are a result of bad water quality, barbels, what seems to you as swim bladder, etc..These are the consequences.
As for Ph, mine are living quite happily in a Ph of 7.4, Kh-8 and Gh-12 so that really isn't the issue with your corys.
 
You've got to figure out why you are getting ammonia/nitrIte readings. If I were you, although it won't help instantly, I would get a second filter in there. It might be yours just can't cope with the bioload in the tank. Don't overfeed while you've got water quality issues, it won't help.
 
Also, when there are water quality issues, you need plenty of oxygen as that's a limiting factor for beneficial bacteria so don't stop/reduce the surface agitation. For you plants you can get some liquid carbon for a start. It's not affected by surface agitation and plants too need oxygen.
Planted tanks would benefit for extra flow too, so getting bigger filter/more filters will be of benefit to all.

 

[DoubleDutch]

I still think it''s due to your feeding behaviour.
 
"1 Female has been plump for a while. The other was somewhat thin from having laid but has plumped up a lot this last week (this is due to feeding less attempting to kill off algae & postpone egg-laying. It worked. I've returned to feeding them well.)"
 
Corys are NO algae eaters, but omnivores being up to 95% carnivores. Less feeding because killing algae is killing your Corys !!!!
They will eat it but they definitily will get healthproblems !!!!! Females need to be plump (full of eggs !!!)
 
Please give them high protein food (bloodworms aso) and let them be Corys again. No Cory no glory !!!

 

[DoubleDutch]

Reading your post again I maybe misunderstood (as a Dutchman) you feeding less to kill of algae. Sorry about that hahahaha.
But it still isn't the way to do that to my believe. Don't underfeed your fish for that reason, especially Corys !! When they get thin, they will have healthproblems. Took some over from someone who gave them a wrong diet.
 
 

Then

 

 

Now

 

[EddyBearr]

The issue is your ammonia and nitrIte reading. My corys will scratch themselves even if the test shows undetectable and that's when I overclean the filters.
You need to do larger water changes when you've got a reading. A 5G water change will remove just 23% of the detected ammonia/nitrIte. Do adequate water changes to remove all of it at once.
All the other cory issues are a result of bad water quality, barbels, what seems to you as swim bladder, etc..These are the consequences.
As for Ph, mine are living quite happily in a Ph of 7.4, Kh-8 and Gh-12 so that really isn't the issue with your corys.
 
You've got to figure out why you are getting ammonia/nitrIte readings. If I were you, although it won't help instantly, I would get a second filter in there. It might be yours just can't cope with the bioload in the tank. Don't overfeed while you've got water quality issues, it won't help.
 
Also, when there are water quality issues, you need plenty of oxygen as that's a limiting factor for beneficial bacteria so don't stop/reduce the surface agitation. For you plants you can get some liquid carbon for a start. It's not affected by surface agitation and plants too need oxygen.
Planted tanks would benefit for extra flow too, so getting bigger filter/more filters will be of benefit to all.

The ammonia & nitrite readings were due to a recent die-off of plants due to algae (and then algae due to tackling the algae,) but the plants are getting back to normal.
The two females who had symptoms stopped showing them after having peas. The small male didn't eat the peas as much but has definitely doing better (though still a concern.)
The filter is pretty strong for the tank size, and the bioload is pretty small.
 
The females are getting their barbels back, but I'm not so sure on the small male.

I still think the abnormal cory behavior was from overfeeding, but I'll be keeping an eye out.

@DoubleDutch: Yeah, I was just trying to cut back on food to prevent algae from occurring due to excess nutrients. I still fed the cories enough to "sustain them" as they were, whereas normally I feed them pretty well so they might lay eggs.

And yeah, I gave them some bloodworms the other night, and when the lights went out, they started swimming all over. They loved it.