Desperate for Help....Green, cloudy water and fish dying.

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Micco73

Aquarium Advice Newbie
Joined
May 20, 2025
Messages
7
Location
New Jersey
Good Morning All,
I have a 75g Freshwater tank, 3 years running well. About 3 months ago, my filter went, and I bought a replacement. I t is a typical dual Marineland filter that hangs inside the tank. Since I replaced it, my water has consistently been cloudy & green. I checked the water, and all my levels seemed on point, despite it looking very bad. I have done water changes, added coral, and followed several recommendations, with little, to no success. I have plenty of oxygen, and water flow in the tank. I did a 50% change yesterday, and just received a text from home, that two fish have died, and another seems to be struggling....can someone please help with some solid advice, I need to help my fish.
 
What precisely are the water parameters?

What is a typical water change schedule? How much, how often?

Green water is typically caused by too many nutrients, and too much light. So we go back to water parameters, and how long is the aquarium light on for? And is the aquarium anywhere near natural daylight?

The dead fish and the green water may be unrelated. What species of fish are we talking about, and are there any symptoms? Can you post a photo of the fish, or better still upload a video to YouTube and post a link.
 
I will gather all the detailed info when I get in from work. Typically, the light is on from about 8am until about 8pm. I have 2 separate led lights that hang over the tank, and yes, there is a large window in the room as well. Not sure which fish perished, my Wife is not aware of who is who. I have Angel's some Molly's, a gourami, and several catfish. I checked the water a week ago, and everything was in a good range. This is really frustrating me, I don't want the fish to suffer, due to something I'm doing, or not doing. This all started, after I changed out the filter about 3 months back, someone suggested that I upset the good bacteria and threw everything out of whack.
 
Your light is on way too much, and you really want aquariums as far from natural light as you can get it, or have curtains/ blinds closed. Cut the aquarium light down to 6 hours a day, and do something to reduce the natural daylight.

What precisely are the water parameters? Saying good range isn't helpful. I've dealt with 100s of hobbyists who say their water is good, but when they come up with numbers they aren't. Sometimes people have said their parameters are good when they haven't even done a test.
 
See if you can post the photo/ video of the sick/ dead fish. While changing the filter could easily have effected those bacteria you mentioned, that was 3 months ago and the new filter should have cycled by now. So if your water parameters are good we need to look at another cause.

We should also consider that even if your aquarium is cycled, it may not have been for a period after the filter was changed and the water parameters at the time may not have been good. Poor water quality can have an effect on fishes health long after the water has been cleaned up.
 
I checked my water after work last night, Ammonia was very high, at a 4. I added some Fluval Bio enhancer and will be keeping the lights off as much as possible. I cut back on feeding as well. I only lost a single Angel fish, I think my FIL's eyes are going, and the rest seem active and OK. How long do you think it will take for things to straighten out?
 
There is the cause of all your problems.

High ammonia will be fuelling algae growth and is toxic to fish at the level you are reporting.

See how important to report actual numbers rather than saying everything is good? If nothing else, the need to report parameters made you check them and led to the issue.

What are your other parameters? pH, nitrite and nitrate? General hardness and carbonate hardness would be useful too. What test kit are you using?

The bio enhancer is Fluval Cycle? That's a waste of money. In scientific, peer reviewed studies of these products the only ones that showed any benefit compared to using nothing where FritzZyme #7, Fritz Turbostart 700, and Tetra Safestart. Dr Tims One and Only is essentially the same product as Safestart as they where developed by the same guy. If you arent using one of those products I wouldn't waste your money. May as well use up the Fluval product now you've bought it, but it probably won't do anything useful.

What you need to do as a matter of urgency is get the ammonia down below 0.5ppm. You do this through water changes. Based on a starting point of ammonia at 4ppm that is going to take 3 x 50% water changes. Do them a couple of hours apart, but don't put it off.

I would recommend using Seachem Prime or API AquaEssential as your water conditioner for these water changes as they will both give some protection against the toxic water conditions. But don't rely on them to do all the work. The only sure fire way to get the water safe in your circumstance is water change after water change until the toxic parameters are safe. If you don't have Prime or AquaEssential still do the water changes with whatever water conditioner you have, but get one of those as soon as you can.

Once you've got the water to a safe level then we can look at getting your aquarium cycled. That will involve a lot more water changes over the upcoming weeks.

What water conditioner do you usually use?

How long will it take for your problem to sort itself out? It typically takes a couple of months to cycle an aquarium. But yours has already been 3 months, so something else is going on. Knowing those other parameters will help. You say you have a 75g aquarium, but how many fish are we talking about and what species? Your new filter, what model is it precisely or can you post a photo of it, and maybe I can figure it out.

The green water/ cloudiness will clear up over time once you are cycled and got the lighting under control.
 
First off...thank you for taking the time to provide such a detailed & informative response. I'll try to respond in order of your comments.
Test kit is an API Freshwater Master kit.
While I do not have numbers, the PH, Nitrite & Nitrate, were all in the optimal range.
I will order one of the products you recommended and will do a 50% water change this evening, I also did one last Sunday. My work schedule will only leave me time for one water change a day; I can do more on the weekends if needed.
I currently have a total of approximately 20/25 fish. An Angel, 2 gourami's, several mollies & platys, several catfish, 4 algae eaters & a pleco.
 
Again. Stop with the "good" and "optimal". It's not helping. Actual numbers every time, or "I'll let you know" and update later. I have no idea if you understand what is a good parameter, you thought the ammonia was good. Knowing all your parameters will help. Eg, a pH below 7 makes ammonia less toxic, pH above 7 makes ammonia more toxic. The reverse is true for nitrite. The presence of nitrate will give a clue as where you are with your cycle.

Do you go to the doctor and just say im fine and hope they can somehow diagnose what's wrong with you?

Go through the posts and give answers to all the questions posed when you are able.
 
OK, while I appreciate the help, your delivery needs serious work. This is new & overwhelming to me. If you are going to speak down to me and make me, feel stupid for not having your level of experience, I'll take my problem elsewhere. I am doing the best I can with the time I have available. I have had this tank for 3 plus years, without issue, so this new development is stressing me enough, without the added judgement. Thank you for the advice, and have a good day.
 
OK, while I appreciate the help, your delivery needs serious work. This is new & overwhelming to me. If you are going to speak down to me and make me, feel stupid for not having your level of experience, I'll take my problem elsewhere. I am doing the best I can with the time I have available. I have had this tank for 3 plus years, without issue, so this new development is stressing me enough, without the added judgement. Thank you for the advice, and have a good day.
With all due respect, ( and speaking as a former fellow Jerseyite ;) ) Aiken is not talking down to you. You are taking his comments in a wrong way. Keeping fish ( or any animal) is not easy. Things happen that can throw an aquatic environment out of whack. The problem is that the whole system is interconnected. It's a big " If this is happening then that is the cause." So if you don't have all the numbers, we only know the if and not be able to determine the cause.
I've kept fish for 60 years and was in the pet business for over 45 years ( starting in NJ. ) and I've seen all kinds of experiences. They range from success without any knowledge of what was happening at all to catastrophes because people were doing too much to their tanks and killing everything off. So this is why the more information you can provide by answering the questions, the better we can help you. The fact of the matter is that there is no such thing as a blanket "good" or "optimal" that will fit all the different fish species we keep. Even when you see the information online about a specie where it says the fish can live in a range of temperatures, people don't seem to understand that the extreme edges of the those are only for temporary periods and not full time. So when the fish has a problem in that extreme temperature, it puzzles people because the online info said it could live in that temperature. See what I'm I'm getting at?
You said in your first post that the tank has been running for 3 years. You should have learned a lot in those 3 years so your comment "This is new & overwhelming to me." is a little puzzling. So let's go back to the basics:
How often do you do water changes?
How much do you change when you change water?
How often do you clean your filter(s)?
How do you clean your filter(s)?
What is your Tap Water's parameters?
What do you do to your replacement water before adding it to the tank?
Let's start there. (y)
 
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