It might, I've been careful because I am slightly over stocked as it is so I don't want to add in too much extra ammonia. But I'm not sure of what kind of light to get or if there is a "too bright". Lights are kind of expensive so I want to get good ones the first time around.
40ppm is fairly high, you should have algae. If you find your nitrates high, always reduce them slowly. I've seen a lot of cases of nitrate shock and poisoning recently.
What is your set up?
3 goldies and one BN pleco. One filter atm but planning to add an additional one to bring the total up to about 700 gph. I mean, there is definitely algae as the pleco is eating something but she is a tiny little pleco.
The fish themselves seem just as happy as ever. I actually ended up changing the water because the nitrites and ammonia were a bit high.
I am thinking of getting some brighter lights but at 20$ a light and I need two ._. So kinda stuck atm. There is a window in the room but the problem is the 20g with the betta is literally right in front of it so I'm not sure if it'll be okay for him to get so much light.
What I would recommend is rather than a filter is you purchase a water pump, or pond pump (not air pump or bubbler). To oxygenate a goldfish tank you need heavy surface action, you'd need one about 500gph. If you have a lid on the tank remove it. This way your tank will be oxygenated and should grow algae no problem provided it's cycled.
If you have ammonia and nitrite, then what is your source of nitrate? Normally only see high nitrates in cycled tanks, unless it's in your tap water.