Green Water and Dying Fish

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emincianc

Aquarium Advice Apprentice
Joined
Jun 3, 2024
Messages
10
Location
USA
Help! I have had a community freshwater tank set up for a few months now with no issues. A few days ago the water turned very very green. I used API Algaefix and two days later 4 fish were dead. I don't have exact numbers in front of me but there is no ammonia or nitrites. Hardly any nitrates, ph is around 7.6-7.8. pretty sure when I get home they'll probably all be dead at the rate they're dying. I want to be able to save as many as I can.
 
Help! I have had a community freshwater tank set up for a few months now with no issues. A few days ago the water turned very very green. I used API Algaefix and two days later 4 fish were dead. I don't have exact numbers in front of me but there is no ammonia or nitrites. Hardly any nitrates, ph is around 7.6-7.8. pretty sure when I get home they'll probably all be dead at the rate they're dying. I want to be able to save as many as I can.
It's highly unlikely that you have low nitrates and high algae as the algae needs to have the nitrates to exist. Get accurate chemistry values and we can go from there. (y) That said, a tank only a couple months old shouldn't have a lot of nitrates unless the fish are over fed or there have been dying animals in it as nitrates are the end product of ammonia in aquariums. Does the water you use for the tank have high chloramines or nitrates in it? :unsure:
 
I will recheck the nitrates when I get home. I haven't done a water change this month yet but I normally use gallons of distilled water when I do. I was hoping the algaefix would help the green enough I wouldn't have to do a huge water change but it's been 2-3 days and no change so I am going to do a 50% water change today.
 
Just do a quick Google search on "algaefix killed my fish". Its a common issue.
Oh no. I didn't even look it up, I just assumed being API brand that it'd be safe. Is there a way to fix this or will I likely lose them all?
 
The water change will probably help.

As far as im aware the chemical reactions that algaecides go through deplete the water of oxygen. So its not so much the chemicals are toxic, but the side effects that cause problems, especially if you arent careful on how its used. So aquariums with high O2 content will be less likely to have issues than ones with low O2 content. Overdosing algaecides is risky.

Really every time you add chemicals there is a risk. As with most aquarium product manufacturers, API sell a number of products that dont do what they claim, or fix problems that dont exist, or are downright harmful. Their only purpose is get you to spend money on stuff.
 
Would you all recommend a 50% change with only distilled water? Or could I get away with 25% distilled and 25% regular water? Not trying to buy almost 30 gallons of distilled water if I absolutely do not have to.
 
You know your water chemistry better than me.

Are you remineralising your distilled water when you do a water change?

Why are you using distilled water for your water changes?

Are you commonly mixing distilled water with tap water when you do water changes or using just distilled water?

If you do use any tap water in your water change make sure you use a water conditioner.
 
I originally started with just tap water and used a bacteria starter and a water conditioner. It was recommended to me on another forum to use distilled water rather than tap since the tap could be too rich. This is all new to me still. I had just been doing 25% distilled water only changes.
 
Distilled water is bad for aquariums on its own. It doesnt contain any of the minerals etc necessary for a healthy aquarium. It has zero (or at least very low) general hardness (GH) which would suit fish that prefer softer acidic water, but wont suit fish that like harder, higher pH water. It also has zero (or at least very low) carbonate hardness (KH) which can effect your aquariums ability to cycle, might effect plant growth, and will provide no buffering against pH fluctuations which are bad for fish.

If you use distilled or RO filtered water you need to add those minerals and carbonates/ bicarbonates back into the water. Normally this is done by adding buffering salts, or you can mix distilled with tap water so it gets those minerals from the tap water proportion. This is commonly done when you need to tailor very specific water parameters for your fish, or if your tap water is very hard and you need to soften it.

I cant comment on what was discussed on another forum as to what lead them to suggest distilled water. Nothing you have raised so far on this thread leads me to suggest distilled water is necessary, but maybe you provided information to this other forum you havent done here.

While this may not be related to your fish deaths it is something that should be considered. The lack of minerals may have caused an unhealthy environment for your fish. The lack of KH may have lead to fluctuating pH levels that stressed the fish. Maybe the addition of algaefix compounded issues.

Ive done a little reasearch on how algaefix works. It does indeed use a lot of oxygen in the process of killing algae. Lots of algae die off, more oxygen depletion. Did the algaefix have any positive effect on your algae?
 
Distilled water is bad for aquariums on its own. It doesnt contain any of the minerals etc necessary for a healthy aquarium. It has zero (or at least very low) general hardness (GH) which would suit fish that prefer softer acidic water, but wont suit fish that like harder, higher pH water. It also has zero (or at least very low) carbonate hardness (KH) which can effect your aquariums ability to cycle, might effect plant growth, and will provide no buffering against pH fluctuations which are bad for fish.

If you use distilled or RO filtered water you need to add those minerals and carbonates/ bicarbonates back into the water. Normally this is done by adding buffering salts, or you can mix distilled with tap water so it gets those minerals from the tap water proportion. This is commonly done when you need to tailor very specific water parameters for your fish, or if your tap water is very hard and you need to soften it.

I cant comment on what was discussed on another forum as to what lead them to suggest distilled water. Nothing you have raised so far on this thread leads me to suggest distilled water is necessary, but maybe you provided information to this other forum you havent done here.

While this may not be related to your fish deaths it is something that should be considered. The lack of minerals may have caused an unhealthy environment for your fish. The lack of KH may have lead to fluctuating pH levels that stressed the fish. Maybe the addition of algaefix compounded issues.

Ive done a little reasearch on how algaefix works. It does indeed use a lot of oxygen in the process of killing algae. Lots of algae die off, more oxygen depletion. Did the algaefix have any positive effect on your algae?
All parameters were considered normal except for the water hardness. It was very hard so it may have been suggested as a way to soften it. Since doing that we've had no issues with ph or anything really until now. The algaefix did absolutely nothing other than kill the fish. Maybe I'll try a mixture of tap and distilled since all tap the first time made he water too hard, I don't want to end up there again.
 
Yes. Distilled water will soften tap water if mixed with tap water. If its just used on its own you will be swapping very hard water for very soft water which might be better or worse depending on what fish you are keeping.

If you are suffering from green water, this is the result of too much light combined with too many nutrients. Is your aquarium sat in direct sunlight or close to a window? How long are the aquarium lights on for?

If you really want an effective way to kill off the algae, assuming you dont have live plants read post #8.

 
No live plants. The tank lid has an LED light that was left on for most the day, daily. Since the water turned green I have kept it off at all times but it does sit near a window. Not directly but close enough.
 
Yeah. You dont want aquariums anywhere near a window. Opposite side of the room.

To give you an idea on how light falls off the father away it is from a window i happen to have a lux meter with me. Outside 10000 lux, inside on the window cill 1000 lux, on the opposite side of the room 5 lux. Light levels really drop rapidly when you move away from the window even if your eyes dont notice the difference too much. You really dont want aquariums anywhere near a window.

And aquarium light, no more than 8 hours per day.

A complete blackout should kill off algae quite quickly, controlling the light levels should reduce algae but it will take a long time. If you dont move the aquarium away from the window you won't solve your algae problem.
 
Yeah. You dont want aquariums anywhere near a window. Opposite side of the room.

To give you an idea on how light falls off the father away it is from a window i happen to have a lux meter with me. Outside 10000 lux, inside on the window cill 1000 lux, on the opposite side of the room 5 lux. Light levels really drop rapidly when you move away from the window even if your eyes dont notice the difference too much. You really dont want aquariums anywhere near a window.

And aquarium light, no more than 8 hours per day.

A complete blackout should kill off algae quite quickly, controlling the light levels should reduce algae but it will take a long time. If you dont move the aquarium away from the window you won't solve your algae problem.
We do plan on moving it into the basement but just not at that point yet. We're still finishing it. It currently sits in our living room on the wall next to our glass back door, and there is a window on the other side of the room. I'll try keep the light off 24/7 still and wrapping it in black trash bags. Thanks for the help!
 
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