Unusual light set up. Too much light, or too little. How to adjust my mistakes in lighting

[Kizmet]

I have two newly set up low tech planted tanks, they are identical second hand models (old fluval 10gallon tanks). With single 15w t8 light fittings. The first tank I set up I put an Arcadia tropical bulb in and many of my plants grew leggy and died very quickly. I have changed many species and they are now surviving and after 4 months algae is under control. My second tank has been set up for a week as a moss wall divided betta tank. As I needed a covered tank and I have no way of modifying the hood I have stuck a desktop led grow lamp shining into the sides and a cheap full spectrum daylight t8 in the hood. The plants are all growing well but the hair algae is awful after just a few days. The led grow lamp has turned out to be 50w. Are there ways to fix the imbalance without adding c02? Would having the grow lamp on for a couple of hours instead of 8 be enough for my plants and just have the t8 for the rest of the lighting cycle?

 

[Matt @ ScapeEasy]

Bit confused by this...
You have 1 tank running successfully with a 15w bulb?
Another tank with a 50w bulb shining on the side and a 15w on the top?

Why not just use the 15w bulb and similar planting as the other tank? Sorry I'm clear misunderstanding something here...

Reducing lighting duration will help combat a light thata too powerful but 15w to 50w is quite a difference, tho it depends on the bulb outputs in terms of par etc of course, it aounds like the bulb ia too powerful altogether to me for a tank of that size.

 

[Kizmet]

Yeah, sounds a bit stupid doesn’t it. The 50w is a cheap led grow lamp not designed for aquarium use, I had heard they were generally rubbish and figured it would add just enough to get my mosses growing. It obviously works, just with this algae side effect. The main reason I added the light was because moss has failed miserably in my low light tank and I wanted a moss dividing wall. In the low light tank the java fern, frogbit and Anubias are the only successes,