90 Gallon Aquarium Crashed

[FishStix]

90 Gallon Aquarium setup 6 months ago

Weekly water change

Substrate sand

Filter Fluval FX6

Temp 79

Ammonia - 0, Nitrite - 0, Nitrate 5, pH-6.90 

No changes to tank, other than it started to get very cloud and pH was dropping (i do buffer with crushed coral as we have low KH)

The next day pH dropped to around 4.50, and most of the angels in the tank died, platys were fine.  I then replaced the crushed coral and did a water change.   The pH is back to normal and seems somewhat stable again, but this was 2 weeks ago, and the tank is very cloud and won't seem to go away.  Everything is testing normal.

I don't know what else to do at this point, i have confirmed no dead fish remain in the tank or the filter.

Any suggestions?

[Hobbit]

Yikes. Sorry to hear about this! Especially the loss of your angels. ❤️

To get a pH swing like that, it sounds to me like your KH is way too low. I also have really soft water and I recently got a GH and KH test kit. It showed me that supplementing with crushed oyster shell in my 55 gallon wasn’t increasing my hardness enough. I’d recommend getting a kit if you don’t have one already, just to check that your crushed coral is getting you where you need to be. I add cichlid salts, baking soda, and crushed limestone in small amounts as well as using the crushed oyster shell.

As for why the tank is still cloudy, it’s probably just the tank re-establishing the cycle. Hopefully the cloudiness will go away before long.

One other thought—do you have well water? I know my well water changes pH as the year goes on depending on rain or leaves breaking down or who knows what. Maybe something changed in the water you’re adding to the tank.

[Maggie]

7 hours ago, Hobbit said:

Yikes. Sorry to hear about this! Especially the loss of your angels. ❤️

One other thought—do you have well water? I know my well water changes pH as the year goes on depending on rain or leaves breaking down or who knows what. Maybe something changed in the water you’re adding to the tank.

I heard that the parameters in municipal water supplies can also change dramatically and temporarily if there's a big storm, as they add more chemicals.

[Alesha]

You've gotten good answers here @FishStix. I have super hard water, but the KH tends to swing if I don't include coral AND a Wondershell. Some of my tanks also need occasional doses of Alkaline Buffer, too; but I don't do that until they start to swing to an acidic pH. 

And yeah, I agree that the cloudy water is your cycle reestablishing the bacteria.  So, be patient, check your parameters often, do water changes if the ammonia or nitrite get high. But otherwise, just let it do it's thing. 

Sorry for your fishy losses. Hoping it will do better after this cycle is finished.

[Ruud]

Pretty much what is said here. I would get a kit that measures your KH and GH and do a daily test to see if there are swings. Don't put in more fish until you have stabilized these both parameters. 

Sorry to hear about loosing your fish, that's always heart breaking.