New Fish Dying Help

[usagi9197]

I bought 5 new fish last week. 3 mollies and 2 swordtails. The 2 swordtails have died. One of the mollies doesn’t look too good either. He is sitting at the bottom of the tank. The fish appear perfectly fine one minute and then die the next. I am really anxious and don’t know what to do. I tried saving the remaining fish by taking them back but the store won’t take them. All other fish appear fine accept 2 female danios have a curved tail. That has been going on for awhile though and they are otherwise acting normally. I will say awhile back my tank did get contaminated with bleach. I treated this by using extra strength de chlorine and charcoal. I removed and cleansed source of bleach which was the filter. I did 100% water change over a week. This was months ago though and no other fish have died since. I bought a kit to test for chlorine though to rule it out.

Current set up:
29 gallon tall
6 zebra danios, 1 female swordtail, (new) 3 mollies
Live plants
Black beard algae issue

Chemicals added:
Stability
Flourish Excel
API tap water conditioner
Aquarium salt

API test kit results
No3 200+ (I did a 25% water change)
No2 0
PH 7
Kh 40
Gh 120

API test results after water change
No3 160
No2 0
Ph 6
Kh 40
Gh 180


I have done a 25% water change and added aquarium salt. Any other advice?

 

[Andy Sager]

I see 2 potential issues:
1) Livebearer fish like Swordtails and Mollies do better in higher pH water (7.5-8.0)
2) Nitrates (No3 ) are more toxic in low pH water so in your case, the fish may be responding to both of these issues. They most likely came from a low nitrate environment wherever you got them from then went into a high nitrate, potentially more toxic, environment and couldn't handle the change.

I would also add that the black beard algae issue is most likely related to your high nitrate level. By reducing your nitrate level to under 40 PPM ( the lower the better without reducing it to 0 for your live plants) and keeping it there, that alone can help control the BBA instead of using chemicals. Chemicals won't work if the conditions aren't correct . I suggest doing your 25% water changes daily until you get the nitrates to under 40 PPM before adding any new fish. Make sure you are doing some substrate cleaning as well to help remove any uneaten food or detritus which is adding to your nitrates.

 

[usagi9197]

I see 2 potential issues:
1) Livebearer fish like Swordtails and Mollies do better in higher pH water (7.5-8.0)
2) Nitrates (No3 ) are more toxic in low pH water so in your case, the fish may be responding to both of these issues. They most likely came from a low nitrate environment wherever you got them from then went into a high nitrate, potentially more toxic, environment and couldn't handle the change.

I would also add that the black beard algae issue is most likely related to your high nitrate level. By reducing your nitrate level to under 40 PPM ( the lower the better without reducing it to 0 for your live plants) and keeping it there, that alone can help control the BBA instead of using chemicals. Chemicals won't work if the conditions aren't correct . I suggest doing your 25% water changes daily until you get the nitrates to under 40 PPM before adding any new fish. Make sure you are doing some substrate cleaning as well to help remove any uneaten food or detritus which is adding to your nitrates.

Thank you for the advice. I will continue to do my 25% water changes until my nitrates get under control. I will vacuum the substrate as well. Thanks for your help!

 

[Andy Sager]

Thank you for the advice. I will continue to do my 25% water changes until my nitrates get under control. I will vacuum the substrate as well. Thanks for your help!

 

[Aiken Drum]

One thing to be aware of is that the pre-existing fish will be used to the very high nitrate because it crept up on them. New fish will have gone through a very sudden change in water quality straight from clean low nitrate water into high nitrate water.

Its very common for people who havent kept up with water maintenance and allowed things like nitrate to gradually get worse, to see their fish be reasonably healthy but for new fish not be able to acclimate to the poor water conditions and die.

Whats your normal water change schedule like? How much, how often? You arent really heavily stocked so a small weekly water change, or moderate fortnightly change should be enough. If you are already in a fairly good habit of changing water, whats the nitrate in your tap water like?

 

[usagi9197]

I suffered from serious depression and neglected my tank for months. Now I do water changes about once a month since the load was so low. I’m going to be doing 25% every day until the nitrates get under control. Then I will do it once every 2 weeks. That’s the plan anyway.

 

[Aiken Drum]

Once you get nitrate under control Id probably look to be changing half the water every 2 weeks, or 25% every week to keep it there. If you add any more fish to what you mention above, id look at 30 to 50% every week depending on how many more you add.

 

[usagi9197]

Once you get nitrate under control Id probably look to be changing half the water every 2 weeks, or 25% every week to keep it there. If you add any more fish to what you mention above, id look at 30 to 50% every week depending on how many more you add.

Thanks for the advice. I didn’t realize I needed to do it so much or so frequently. I will likely end up doing a 30-50% change every 2 weeks.

 

[Aiken Drum]

I see a lot of online advice telling people they need to change 10 to 15% every month. What that normally leads to is where you are now which is sky high nitrate and whats called "old tank syndrome". You wont notice anything wrong because your fish become acclimated, but when you add new fish that arent acclimated, the new fish die. And the fish store gets blamed for selling unhealthy fish because "my other fish are fine". Over time living in such high levels of nitrate isnt healthy anyway even if acclimated, and will catch up with the fish eventually.

You can keep aquariums with very low water change schedules, or even zero water changes. But you usually have to do things differently to compensate. Low numbers of fish, lots of plants, high nutrient demand plants, or other ways of controlling harmful stuff that builds up over time if you arent changing water. Just not changing water is rarely successful.

 

[Andy Sager]

I suffered from serious depression and neglected my tank for months. Now I do water changes about once a month since the load was so low. I’m going to be doing 25% every day until the nitrates get under control. Then I will do it once every 2 weeks. That’s the plan anyway.

One thing to add, the " load" of the tank is not really the criteria for water changes. Different fish absorb the minerals in the water at different rates and some are messier than others so it will depend on what kind of fish you have which will determine how often you should be changing water. Unfortunately, there is no "thermometer" you can use to test the fish to see how much they are absorbing so changing water more frequently solves the issue of the unknown.
As for how much to change, large volume water changes can be both helpful and harmful. Too large a change too fast can cause issues with the fish. In order to safely do large volume water changes you need to make sure your water parameters in your replacement water are similar or close to what your tank water is regarding pH and temperature. You will want the nitrate level to be 0 or very low in your replacement water and check for the amount of ammonia in the water after using a water conditioner if your water contains chloramines.
I know it sounds overwhelming but it really isn't. Just like you do a simple mental checklist when you get into your car to drive it, you do some simple steps before changing large volumes of water. Personally, I like smaller changes more often ( weekly or twice a week depending on the fish being kept) but sometimes larger volumes are necessary.

 

[usagi9197]

I see a lot of online advice telling people they need to change 10 to 15% every month. What that normally leads to is where you are now which is sky high nitrate and whats called "old tank syndrome". You wont notice anything wrong because your fish become acclimated, but when you add new fish that arent acclimated, the new fish die. And the fish store gets blamed for selling unhealthy fish because "my other fish are fine". Over time living in such high levels of nitrate isnt healthy anyway even if acclimated, and will catch up with the fish eventually.

You can keep aquariums with very low water change schedules, or even zero water changes. But you usually have to do things differently to compensate. Low numbers of fish, lots of plants, high nutrient demand plants, or other ways of controlling harmful stuff that builds up over time if you arent changing water. Just not changing water is rarely successful.

Thank you for the advice. I have a planted tank but I will do more water changes and I think that was the issue. No more fish have died

 

[usagi9197]

Just posting here to say thanks to everyone that helped! I’ve been doing pretty aggressive water changes and no other fish have died. So if anyone comes across this high nitrates can and in some cases will kill for fish.

 

[Andy Sager]

Just posting here to say thanks to everyone that helped! I’ve been doing pretty aggressive water changes and no other fish have died. So if anyone comes across this high nitrates can and in some cases will kill for fish.

Glad you got that straightened out. Yes, nitrates are thought to be harmless but in reality, their level of harm is dependent on other factors like pH and the types of fish one is keeping. As with most things fish keeping, there are no blanket answers past " It depends. "