Mature tank keeps getting yellow tint

Ok so the last two weeks or so my 200l tank has a yellowish tone to it.
All my fish seems ok but it's my display tank a d the yellow water seems unsightly.

I have 5 tanks and it's the only one with this problem.
Ammonia is 0
Nitrites is 0
Nitrates >20
Temps 25
PH unknown
Hardness unknown
Tank is set up for about 3 months now.

Stock is
3x Black mollies
2x Platties
2x Angels
1x betta female
1x indian glass fish
And about 15x guppy males

I do at least 60% water change weekly.
I feed only twice a day as much as they will eat in 2-3 min
No Driftwood or live plants
Hob filter that is designed to do up to 300l tank
It's really frustrating.

 

Any smell from the tank?

 

No odour at all not even a fishy smell.

 

Put some seachem Purigen in the hob, it will sort it out. The yellow tint is dissolved organics, Purigen is designed to take it out. My Oscar tank loves to go yellow, after I put purigen in my filter it was gone.

 

Thanks Boelder I'm definitely going to try it.

 

It works beautifully, bit pricey to begin with but it lasts a long time and you can re-activate it a couple of times. It really works. Get a baggie of purigen, do a water change and put it in the back of the hob somewhere, crystal clear water for a long time. Another good product is seachem pristine. I was skeptic about it but it also works. It's bacteria that breaks down organics and gunk. I use it in my discus tank to keep the filter pipes clean, nothing worse than having brown blowback from a filter after you made the tank spotless haha. I don't use it often, only when I see my pipes getting a build up. You probably don't need pristine but it's good to know about it for future tanks and such.

 

@Ladysphinx , not sure if this is relevant but a while back i had a tank with mollies, swords and platys and that tank kept doing the same thing all my other tanks are crystal clear

I since let go of it but if i think back, that tank was close to a window or actually in front of a window.
Can too much sunlight maybe do this?

I do agree with BoelderBeestie, Purigen is a little expensive to start but magic

 

Agreed.
Purigen all the way.

 

Interesting mention, my tank gets morning sun from around 6 o'clock until about 9 o'clock. Problem id I have no where else to move it at this point of time. Maybe Purgen is my best bet right now

 

A pair of blinds or curtains might be cheaper than Purigen

 

Purigen like they said.that stuff is amazing

 

@Ladysphinx I know that yellow you're talking about, my guppy tank gets half day sun for the plants and it goes a slight green after a few days not yellow. My oscar tank receives no sun and goes a slight yellow after a few days. My brother and I even named that color oscar piss kleur haha.

 

If you want to do it on the cheap, activated carbon for a week to 10 days will also remove it

 

Seachem Pristine works like a bomb dont need to clean the gravel every week anymore and with Seachem safe also can slip on water change