Keeping Corydoras

[Ginty]

I seem to have problems keeping corydoras.
Ive had 5 die in 4months.
I have one left. My water paremeters are
Chlorine. 0
Ph. 8.0
Kh. 15°d
Gh. 8°d
Ammonia. 0
Nitrite. 0
Nitrate 25
Teperature is. 25.2°c

I feed them catfish pellets monday,wednesdays and fridays and i feed my other fish hikaria tropical fish micro pellets.
I only have one peppered cory left. I want to get him some friends but im now scared because there is obviously something im doing wrong.
I have two platties, two guppies and 3 danios in my 110 litre tank.

What am i doing wrong please guys?

 

[Ginty]

They all seem to die the same way. They start swimming deformed. The last one i found ill was just floating upside down on the top of the water. I boiled some frozen peas and popped the skin off. By the time i did that it had died in the hospital tank.

 

[Byron]

Your pH is a bit high, but for the peppered cory (Corydoras paleatus) I wouldn't expect this to be the issue.  GH at 8 dGH is fine, and that is actually more important.  Temperature at 25C/77F should also not be the issue as this is not too warm (some cory species need it a tad cooler).
 
Your nitrate is high at 25 ppm.  Corys are highly susceptible to any nitrogen, be it ammonia, nitrite or nitrate.  I would work to lower nitrate below 20 ppm and preferably no higher than 10 ppm.  Now having said that, I suspect there may be something else.  High nitrate will slowly weaken the fish, and this affects other physiological processes too.  So what I am suggesting is that the nitrate is contributing more than causing, probably.
 
How often are water changes, and what percentage (volume) of the tank?  I have found this crucial to cory health.  Vacuuming the substrate during these is good too, as corys naturally spend much time in close contact with it.  Have you noticed any barbel erosion or issues?  What is the substrate?  Is there lots of cover (chunks of wood and plants are best for this)?
 
How you acclimate corys to the tank can be critical, but if they are living four months this is less likely; though internal damage done earlier can cause trouble down the road.
 
Do you know if the corys in the store where you acquired these are dying?  Sometimes this can suggest a problem with the fish themselves.  Eratic swimming followed by lethargy and gasping then death can be caused by a number of things, so it is sometimes necessary to explore everything.
 
Byron.

 

[Ginty]

I do a 50% water change every other saturday. I have white stones as my gravel. And i always clean the gravel with a vacuum as i syphon my water out.

As for my nitrate. I use nitrate minus by tetra as my tap water is 30ppm. I currently have one plant and lots of artificial ones. I do intend to get some more easy to care for plants in the near future when i get some spare cash.
Im not aware of any deaths at the petshop. But i have got them from the same shop.
I also leave the fish in the bag floating in the tank for 20mins. Then i add some of the tank water to the bag and leave it for a further 20mins. Then i carefully gt the fish out of the bag and into the tank and throw the water in the bag away. I leave the light off for 24 hours.
I do a 50% water change every other saturday. I have white stones as my gravel. And i always clean the gravel with a vacuum as i syphon my water out.

As for my nitrate. I use nitrate minus by tetra as my tap water is 30ppm. I currently have one plant and lots of artificial ones. I do intend to get some more easy to care for plants in the near future when i get some spare cash.
Im not aware of any deaths at the petshop. But i have got them from the same shop.
I also leave the fish in the bag floating in the tank for 20mins. Then i add some of the tank water to the bag and leave it for a further 20mins. Then i carefully gt the fish out of the bag and into the tank and throw the water in the bag away. I leave the light off for 24 hours.
https/www.dropbox.com/s/nfsas96dxfh7oaf/20141028_190314.jpg?dl=0
Heres a pic of my tank

 

[Ginty]

https/www.dropbox.com/s/sm2drl2s9t8s982/20141028_201351.jpg?dl=0
https/www.dropbox.com/s/zqqpuhr2vva8wgn/20141028_201353.jpg?dl=0
https/www.dropbox.com/s/8llvbwfdytonmiy/20141028_201405.jpg?dl=0
Heres my last remaining cory. It seems to be acting funny now. It lays on the bottom but keeps rising up. So i fear this one is on it way out too. Ive put him in a hospital tank with some crushed skinless frozen peas.

 

[Byron]

The only external thing I can spot from the photos is the sunken belly; corys should be rounded, or at least flat across the bottom.  There is a distinct curvature inward here.
 
This species is commercially raised and not wild caught, so that would lead one to expect fairly well fed fish; wild caught fish might not be eating well, which is the difference with this item.  So that means that this could well be some internal protozoan.  This was why I asked about the store corys, as they would carry it to, but of course after four months they have probably sold them all.  I have no where near the knowledge on disease to suggest anyting, but I will say that three times in the past two years I have had internal protozoan issues with fish, and all were commercially raised; my wild caught fish have never brought disease with them.  Quarantining is wise these days, for at least 4-5 weeks, though again that would not have picked this up now that it is close to four months before it started.
 
I don't know the Tetra nitrate minus, but I would certainly reduce the tap water nitrate somehow.  And up your water changes to once every week, still 50%.  This will help the fish regardless of anything else, and help reduce tank-caused nitrate additions.  Live plants help, and some floating plants are easiest to handle and will take up more ammonia which then doesn't make the journey to nitrite to nitrate.  Plants do not take up nitrate, as some will still say, unless ammonia/ammonium is no longer sufficient, as it takes the plant more energy to change the nitrate back into ammonium in order to assimilate it as their nitrogen.
 
You might want to consider sand for the substrate if you stay with corys.  This fish sifts sand through their gills, extracting microscopic food bits, and that is rather difficult if not impossible with gravel, and this would damage the gills anyway.  Sand is also better for the barbels.  I use play sand, it is inexpensive, smooth, and resembles the sand in many Amazonian streams so it looks quite natural.
 
Your acclimation procedure is good.  The only issue that might occur here is that it is easy to injure fish with nets and bags; I've done this, and the internal injury would not be obvious until the fish begins acting odd.  I'm not suggesting this is your issue, as all five corys would be quite a coincidence.  Just something to know.  It can take a while to carefully net out fish but it is worth not hurrying; some people do the acclimation in a square shaped bucket, which can make netting out the fish easier.
 
I'm sorry I can't pinpoint the issue, but I hope my observations on various possibly contributing factors has been useful.
 
Byron.

 

[Ginty]

I dont think ill continue buying them because it wouldnt be fair to the fish.
What i do know is. When they catch them at the petshop. They really do rush it. So maybe they have injured them catching them. Because they are quick they really do prod about in the tanks. I dont think ill buy anymore from that store.

 

[Ginty]

Also. Would you say maybe i need to feed more? My danios are very greedy

 

[Byron]

Also. Would you say maybe i need to feed more? My danios are very greedy

I would feed healthy fish once a day, omitting one or two days a week (water change day is one to not feed, not before anyway, but a couple hours after is OK).  So your three times a week is not far from this, and sufficient for mature fish (as opposed to fry that need more regular feedings).  But, if the upper fish are getting most of the cory's sinking food, you may need to alter your schedule.
 
I feed both upper and substrate fish together, so the upper are working on the floating flakes/pellets while the lower have sinking foods.  With some fish, like barbs and danios and some tetra, they will still grab sinking foods.  A trick to get around this is to feed the sinking foods at night, at least an hour after the tank has been in complete total darkness.  That means, no room lights on.  Fish will only go into sleep mode in total darkness.  But corys are noctural, so they will scamper about during total darkness and readily feed.

 

[Zikofski]

sadly that dosnt work for my Byron when feeding at night the food seems to wake up the sleeping fish, be it smell or something, feed my fish 3x a week sometimes less some times more, i try not to keep to a strict routine feeding spareingly is best, your 25ppm nitrate is fine for corydoras i have kept corys happily in water with over 40ppm nitrate, u say they are rising to the surface do you have any plants? do you dose co2? and do you have any surface movement from a filter or airstone? corys rise to surface t get air, but very rare, shouldn't be often that is usually a sign, u may have had a diseas that has been picking them off one by one as well but had to tell what that is.
 
personally from experience catching the fish quickly is best, as its less stress on the fish rather catch them quick than sit there for 10 mins trying to catch them. but that should be an issue anyway.
 
i feed my fish sinking pellets only put enough in so the fish can't nab at everything thats what i do, u should haft to worry about food going uneaten as the corys will clean up the floor, and my fish never seem to go for food on the floor no idea why. 
 
hope you find a solution and if you don't get any more thats a shame but a smart move as you said poor corys hope it works out tho

 

[Ginty]

sadly that dosnt work for my Byron when feeding at night the food seems to wake up the sleeping fish, be it smell or something, feed my fish 3x a week sometimes less some times more, i try not to keep to a strict routine feeding spareingly is best, your 25ppm nitrate is fine for corydoras i have kept corys happily in water with over 40ppm nitrate, u say they are rising to the surface do you have any plants? do you dose co2? and do you have any surface movement from a filter or airstone? corys rise to surface t get air, but very rare, shouldn't be often that is usually a sign, u may have had a diseas that has been picking them off one by one as well but had to tell what that is.
 
personally from experience catching the fish quickly is best, as its less stress on the fish rather catch them quick than sit there for 10 mins trying to catch them. but that should be an issue anyway.
 
i feed my fish sinking pellets only put enough in so the fish can't nab at everything thats what i do, u should haft to worry about food going uneaten as the corys will clean up the floor, and my fish never seem to go for food on the floor no idea why. 
 
hope you find a solution and if you don't get any more thats a shame but a smart move as you said poor corys hope it works out tho

I only have one plant atm. Its an anbias. (I think thats how you spell it)
I dont use co2. I just brought it as i was told it was an easy plant to look after. Ive just found one of my platties swimming strangely now. So its obviously something wrong in my tank.
Would it be an internal parasite or something?
He isnt swimming to the top. When he is still his body is rising. I dont think he is supposed to be doing it though. Its the first time one of my other fish has been acting this way. What shall i buy?