Plecos Dying :(

[Dandx13]

I have a 55 gal tank that is established and has been for almost 7 months. I had 2 cycled aqua clear filters which i use for this tank. In this tank I have about 25 Neons, 5 Glofish Danio and 10 Glofish Tetra, and 5 peppered cory cats. 
 
I left a lot of things automated and my mom does the daily maintenance while i am at college. She does a 40% water change every week and there has been no problems. I came home for spring break and realized a good amount of algae on the tank and decided to buy an algae eater. I decided on a small 2 inch bristlenose pleco. He seemed fine on the large pieces of drift wood and in the darkness and then after 2 days i saw that he was dead in the corner. I immediately checked the parameters of the water then they were fine. Ammonia-0  Nitrite-0 Nitrate-10. I have never had any problems with fish like that so i thought he might've been sick before i got him. I proceeded to buy a royal pleco from a different LFS and the same thing happened 2 days later. I checked the water parameters and they were the same. I have no idea what happened and looking for any advice 

 

[WILDER]

How long do you climatise your new fish for?
Do you check the bag water for ph so you know how long to climatise the new fish for before adding to the tank?
Did the fish show any symptoms before dying?
 
Sorry for your losses.

 

[Byron]

Another thought is that it could be the fish.  Plecos are frequently not in good shape when they arrive in the stores.  Loricariids is a group of fish that I will never buy unless they have been in the store tank for a couple weeks minimum, and are eating.  Look for active fish that are eating food, and that have a full belly--if it is sunken, do not buy the fish.
 
I also highly recommend quarantining all new fish.  Over the past few years, there has been a noticeable increase in fish carrying internal protozoan, and these are almost always undetectable until the fish start dying which can be days or weeks after acquisition.  Worse still, these protozoan can quickly spread to every fish in the tank.
 
Byron.

 

[Dandx13]

I acclimate the fish simply by floating the bag, which is what i have always done. I leave the bag with the lights off for a few hours periodically adding small amounts of tank water to the bag. I would need to set up a quarantine tank though wouldn't I?

 

[Byron]

I acclimate the fish simply by floating the bag, which is what i have always done. I leave the bag with the lights off for a few hours periodically adding small amounts of tank water to the bag. I would need to set up a quarantine tank though wouldn't I?

 
On the acclimatization, having mixed the water as you do (good) do you then net the fish out?  You do not want the bag water in your aquarium.  This is not the issue here, just mentioning it.  And many don't hold with doing even this much "acclimating."
 
I never used a QT for close on 20 years with never anything other than ich and that only a couple times.  Then about four years ago I started getting issues with internal protozoan.  I now use a 20g QT for all new acquisitions.  Losing half an existing tank of fish was no fun, twice in a row.

 

[WILDER]

I agree with Byron about internal parasites. I bought some pitbull plecs and they had worms were sticking out of there anus.
Only noticed them a few weeks after purchase.
Also agree about making sure there active, eating, and look healthy. Not bloated, or look very thin.
 
Always check the bag water for PH it just helps you to know how long to keep adding water for.
 
Signs of internal parasites are
Long stringy white waste, or clear mucas waste.
Swollen belly, sunken in belly.
Fish will look skinny.
Bent spine sometimes.
Fish will spit food out.
Fish might swim on it's side.
Worms sticking out of the anus.
Red inflamed anus, or swollen anal region.
Later stages bacterial infections, dropsy.