[martym]

I’ve been loosing Rainbow fish. Tank is new 75 gallons. I did fish in cycle being very careful not to let ammonia, and nitrite to get high. Using prime and water changes. Tank cycled fine fish were doing well. I was using Black Diamond for substrate.
Ph 7.4
Gh and Kh very low from tap.
Temp 78f. First batch of fish died (3) about 1 week after cycling. Tested water 0 ammonia, 0 nitrite and 20 nitrate. Did water change and added carbon to filter. Next day 4 more died. Water results the same. Quickly set up a 10 gallon and got the remaining fish in there with aquarium salt. Left them in for 4 days and saw they had started to eat again. I assumed there was something wrong with the black diamond. Took it out replaced with black quartz sand after cleaning the tank with vinegar. Replaced water got the temp stable added fish back in. Lost 2 more. None of my other tanks (4) are having any issues. Any suggestions??

 

[BadFish]

What species of rainbowfish? All rainbows need minerals in the water, theyre not soft water fish. My guess is that is the issue, if they are not otherwise sick, and are eating. Raise the GH.

 

[DBam]

Yup, that's where I would start too. I've started to buffer a little even for soft water species like tetras and dwarf cichlids because otherwise I would have weird deaths of healthy looking fish. Made a huge difference. Most of the rainbows are hard water. Some are soft, but even then they don't want completely soft.

 

[martym]

Lake Kubutu and boesmani. I will some Seachem equilibrium. I am surprised that soft water would kill them so fast.

Thank you!

 

[dino]

Get stability asap. It's a cheap investment with new tanks . Cycled countless tanks .
Also just a thought for the future remember when you switch the fish out to the new tank the bacteria needs fish in the old tank to survive .

 

[martym]

Should have mentioned I did use stability.

 

[BadFish]

In addition to using equilibrium to raise the GH, consider using some crushed coral in the substrate or in a bag in the filter to help prevent PH crashes. Equilibrium will not increase KH. Crushed coral adds a bit of slow release insurance by providing a bit of consistent KH. Baking soda could be used but its easier to mess up and accidentally cause a nasty swing.

 

[martym]

I do have crushed coral in my filter. I find that doesn’t work very well. I think because we have decent Ph from the tap. I measured it to be 7.6 last night. Does cc not need lower Ph to desolve? The remaining 3 rainbows and Cory’s seem ok today. Still think along with low hardness, there was something in the black diamond. I did dose equilibrium this morning after reading the comments above. I have also ordered a 9 pound pail.
Doesn’t look like the rainbows ate though.

 

[DBam]

Crushed coral will still dissolve at 7.6 pH, up until about a pH of 9. It just won't dissolve as fast as it would in more acidic water. The pH and hardness are separate things, and unless you're on well water most of the municipal water in the Vancouver area has next to no hardness, despite moderate pH levels.

 

[BadFish]

Agree with BDam about it dissolving slower, but still dissolving. The crushed coral is more to prevent PH crash if your KH runs out... which can easily happen if youre just running metro Vancouver water, which has barely any carbonate hardness from the tap. If PH does manage to begin dropping, it would dissolve faster. With metro van water being so soft the PH is very easy influenced in any direction. Ph was brought up to 7.6-7.8 or so not too long ago by the water works people adding if memory serves me 20ppm calcium carbonate to the water to help prevent damage to pipes. One degree of hardness is 17.9ppm.

A little bit in your filter is definitely not enough to bring your GH up to 10dGH to keep the fish happy. If you run straight aragonite sand or crushed coral 1-2" thick as your substrate you could likely get away with using less equilibrium but using equilibrium is easy enough.

Corydoras are south american soft water fish, they shouldn't be bothered by the tap water at all. They should handle the increase in GH as long as its not crazy high... the rainbows and corys kind of have opposite preferences for water parameters but should be adaptable if extremes are avoided.

 

[martym]

Thanks everyone. I knew the Cory’s liked soft water, but I need something in there to eat food off the bottom.

 

[martym]

Tested water 0 ammonia, 0 nitrite, 0 nitrate. Ph7.6-7.8. Kh 6, Gh 9. Fish swimming around looking happier. Hopefully they will start to eat soon. Thanks again for your help!

 

[Marten]

I think it’s more likely due to the fish in cycle. Gill damage from exposure to ammonia or possibly nitrite poisoning. I believe salt treatment is good to help a fish recover from ammonia burn, so that may have helped.

Changing substrate might have thrown off the cycle too, so probably best to confirm that you’re still good there.


Sent from my iPhone using Tapatalk

 

[BadFish]

Awesome! How are you managing zero nitrate? Is the tank heavily planted?

 

[martym]

Fairly new water change and yes planted. Just dosed fertilizer last night so I anticipate nitrates to rise. The bio load on the filters right now is minimal. I don’t expect the nitrates to raise too much until I add more fish.