HELP! Plants Dying

[mnc]

I've had this aquarium set up for a year and it's dying and I don't know what to do!

90 Gallons
5 yoyo loaches
4 red eye tetras
10 guppies
1 clown loach

The fish are all well and I have 0 ammonia, nitrates, a pH of 8.4 and I do regular water changes. I have a large canister filter and I keep it clean.

My problem is that my plants are dying and I dont know why. There should be plenty of nutrients from the fish poop, the light is on for 8 hrs (I lowered it to 6 to try and kill the algae but it didn't work) and have aeration. The water is at 25-28 Celsius and I regularly remove dead plant matter but the plants are covered in algae and they are slowly dying one by one.

Please help! Pictures included (I haven't cleaned the algae in 4 days)

[Autumnsky]

What is your water change schedule? How much and how often?

What kind of light do you have and how old is it?

[Caliban07]

Fish poop can’t sustain plant growth on the whole. I wanted it to be true but I tested it long enough to know that it’s not possible. I’d heard this on a number of occasions so I’ve tested it.

Lets rule at carbon first. If you are not using co2 and have soft water (low in carbonate hardness, KH) then you will need to raise the KH. You can do this best using potassium carbonate, potassium bicarbonate or dolomite powder.

For the nutrients the simplest thing to do is get an all in one. For ease, I usually recommend Thrive if you are in the USA and TNC complete if you are in Europe.

Algae is coating the plants because they are dying and releasing substances that the algae feed on. The breakdown of these dissolved organic carbons (DOC) by aerobic microbes remove oxygen from the water. So as Autumnsky has alluded to already, water changes would be wise. Not only do they remove DOC they add oxygen and carbonate hardness as well as other minerals useful to the plants and the system.

[mnc]

1/5 water changes once a week. I manually remove the algae. My light is a 4ft fluval led that I got a year ago.

[mnc]

Thank you! I'm in Canada so I see if Amazon will deliver what you recommend. The plants have been trying so hard to thrive that I feel terrible for them.

[Caliban07]

Originally Posted by mnc

1/5 water changes once a week. I manually remove the algae. My light is a 4ft fluval led that I got a year ago.

You might need to increase those water changes to 1/3 a week.