Sudden Changes in my 75 Gallon

[powerdyne6]

Something is going on in my tank

My 75 gallon tank has been running for about 2.5 years with no issues up until Friday.

12 Yoyo Loaches (added 3 more this past Wednesday)
20 Penguin / Scratched Inpa Tetras

The Loaches have always been energetic, always swimming, always greeting me at the top of the tank for feeding time but this weekend was a different story. They have all been laying on the bottom of the tank not doing much. No more swimming up to the top to eat, no more of that playful energy. This morning I noticed some of them swimming for a brief period and then floating back down to the bottom.

I have kept the same routine for the most part cleaning the tank every 7 to 10 days. Lately I have been cleaning every 2 weeks. During my last clean 2 weeks ago I removed a couple pieces of driftwood and cleaned them as they had some unsitely algae growth on them. They were only cleaned outside with water from the tap and a brush. No chemicals.

This behaviour is only affecting the Loaches and probably 7 or 8 of them and all started showing the same symptoms at the same time. The 3 I added on Wednesday are not showing any of these signs. It is also not affecting any of the Tetras I have in the tank.

I will have to get water parameters later this evening when I am home from work.

 

[powerdyne6]

Update...

Did some water testing last night

PH: 6.8 to 7
Ammonia: 0
Nitrite: 0
Nitrate: 10 to 20 (hard to tell the difference between the 2 colours)

Did a 60 to 70 percent water change

Woke up this morning to more dead Loaches. I have lost 6 of the 9 so far over the course of 24 hours

What baffles me is that they all died on the same day and none of the other fish in the tank are affected.

Not sure what is going on.

 

[Lcc86]

I'm absolutely no expert but if it's only the loaches that are affected it might be that the new coaches introduced something into the tank that mainly affected that species. That is purely a guess based on the information you've given, hopefully someone else can provide more.

 

[powerdyne6]

I'm absolutely no expert but if it's only the loaches that are affected it might be that the new coaches introduced something into the tank that mainly affected that species. That is purely a guess based on the information you've given, hopefully someone else can provide more.

Only logical explanation.

Basically what I noticed is the fish started to swim abnormally (kind of floating around) would float down to the substrate. Lay for a while then start to move around (almost floating) and then back down to the substrate. And repeat multiple times

But.... the 3 Loaches I introduced on Wednesday last week are alive, swimming around like normal, digging through the sand and eating.

And just to reiterate for anyone new reading this the 20 Tetras I have in the tank are eating and acting "normal"

 

[FranciscoB]

Agree that it most likely was something brought with the new fish, even if they looked ok. Thus far, only the loaches have been affected, but that can change. Quarantine should never be skipped, no matter the source or the looks. It is just not worth the risk. Hope things improve.
You don’t need more fish in the 75g. I have 4 yoyo loaches in a 125g (of course with other fish - silver dollars), and I can not imagine adding more. They are very nice, but very rambouctious, and too assertive at feeding time. Few other fish can compete.