5 Gallon Overrun by Thread/String Algae

[BettaNamedPino]

Hi! I'm new to you forums - thanks for having me! I'm looking for some advice for dealing with an epic thread/string algae problem in my tank. I've attached some photos to show the state of my tank for those of you who are able to diagnose. The problem started a couple months ago, with more fine strands of algae, but recently they seem to have evolved into something thicker.

My tank is about 9 months old now. It is a 5 gallon, Top Fin (PetSmart) tank with a built in filter compartment. I'm using the Top Fin brand carbon filters. The tank is overcrowded currently - it has a betta and 5 gold cloud minnows. My local shop suggested a betta with 3 minnows for a tank this size (looking back that seems like too much), but the minnows have bred and well... now there are more. I also have a golden mystery snail in there who is NOT doing well. I'm not sure if its health is related to the algae issue in my tank or not - I posted about that in the Fish Health forum. Oh, and there are some (I think) Malaysian Trumpet Snails which have found their way in on plants. The fish seem healthy to me, all things considered, but I know the amount of animals in a tank this small is a problem in itself and am working on getting a larger tank.

The tank has 2 pieces of driftwood with some java fern and a Fluval Nano for light. The tank used to sit in a relatively dark place, but after a recent apartment move, now sits next to a window in a bright room. It does not get direct sunlight, but I imagine this could be a contributing factor. I've also turned the LED light down from 12 hours/day to 10, but it hasn't seemed to help. I'm just testing the water with an API Freshwater kit and my numbers seem good from what I can tell. I don't have anything to test hardness or anything like that.

pH: 7.6
High Range pH: 7.8
Ammonia: 0
Nitrite: 0
Nitrate: 0

I use tap water and Seachem prime for water changes. I have been a bit lazy about water changes to be honest, but my last water change was probably 60% and the algae started growing back with a vendetta within a day. It grows on plants, gravel, and driftwood. I have NOT taken the gravel out to clean, but do try to vacuum it as thoroughly as possible a few times a month. I HAVE taken the driftwood out and have tried cleaning it off by hand.

Last thing to mention, since I started noticing the algae problem, it seems like my java ferns aren't growing at all and some of them seem to be starting to melt. I used to have a lot of duckweed in my tank that would grow rapidly, but that growth also slowed down and I ended up throwing the duckweed out, worrying it was contributing to my issues. Kind of seems like the algae is stealing all of the nutrients from the java fern to me.

My plan is to get a larger tank to move the minnows to so my betta can have more room to himself. My snail seems like its on its last legs, so I may be looking to get some ghost shrimp to help with the mess soon, but I don't want to add more creatures to a tank that's already overcrowded.

What kind of advice do you have for me? Should I cut the light cycle down even more? Turn the intensity of the lamp down? Move it away from the window? Should I go ahead and get something like some ghost shrimp that might help? Is this an emergency?

I know this was long, but I wanted to provide as much detail as possible so that I can get the best advice possible. Thank you so much for your help!