My fish keep dying off for some reason

[JMarlow89]

Hello! I was wondering if anyone can shed some light on this for me. I am not a novice at owning a aquarium. I have had them for many years. As of now my fish are slowly dying off one by one. This has been happening for the past 6 months. I keep the water clean and all of the maintenance up as well.

Here is what I have:

125 gallon freshwater planted tank.
Fluval FX-5 canister filter/ Fluval 405 canister filter with attached Coralife 9x UV sterilizer.
The water parameters are:

PH 6.8
Ammonia 0ppm
Nitrite 0ppm
Nitrate 40ppm
Temp is 78 degrees

Here is the livestock

1 large angel ( had angel pair but the male died )
2 small baby angels
8-10 neon tetras ( numerous died )
10 black skirt tetras ( 2 died )
4 loaches
6 cory cats ( 1 died )
nerite snails
1 platy
1 discus
1 peacock eel ( dead )

I clean the filters once a month. I have the fx5 as the workhorse mechanical and chemical filter which houses 2 liters of Seachem nitrate reducer, Chemi-pure carbon, poly filters and coarse pre-filters.

The 406 houses all the biological filters. I have Ehiem substrate, the glass cylinders and the bio-foam.

If anyone could help with the possible problems I would greatly appreciate it!

 

[jlk]

Welcome to AA!!!

Let's see if we can try to figure out what may be happening here as it sounds like a tough situation without any clear cut answers.

You mention this starting around 6 months ago. Did you add any new fish and/or plants that were not properly quarantined for a couple weeks around this time or in the months prior to this point? What is your normal water change schedule?

Can you tell us anything in respect to the fish that are now deceased? Were they listless, lacked an appetite, skinny/bloated, sores, spots, fuzzy and/or white patches, gasping, red gills, veining in fins/tail, any type of odd behaviors (not schooling, hiding, whirling/spinning, bottom sitting or floating, etcetc)? Anything at all that may have seemed abnormal or simply a bit odd in any of the deceased prior to demise or after? Any fish presently with anything amiss or any possible symptoms?

This information will help us to help you better!

 

[JMarlow89]

Well, I haven't added any more plants since all of these are growing like weeds. I take out about 15 gallons a week. I don't really mess with the gravel since it's the fluorite with the mud/ goop that is used for the plants.
It all started when I had a mass suicide death of 7 discus within 2 weeks. Then all of the other fish slowly went. They didn't show any signs of anything. The only one that did show anything was the last blue sapphire discus . It had a white spot on it. I moved it to another tank and the next few days it went belly up. I had thought it was a bacteria so that's why I bought the sterilizer. Everything seemed to be back to normal when it was in use but then the bulb went. So for a few months I went without it then the deaths started coming back.
My angel pairs were happy. I would have thought the tank was in good shape since they had almost 20 batches of babies one after the other. Then one morning he was floating. After he died the neon tetras started going one by one. Then the Cory cats. I didn't see anything I'm them because once I found them they had white fuzz growing on them. The eel was swimming and going about his business then one afternoon I found him at the bottom basically white and dead.
Chemical wise I only add flourish excel once a week and flourish twice a week.
I feed them omega one tropical flakes and one in a while the frozen brine shrimp.

 

[Delapool]

Just wondering what your water change schedule is? Only as with the filter cleans I was expecting nitrate to be lower (although it's not a bad number).

Edit - sorry just re-reading and 15gal per week pwc?