oks...from what I can see you have a few different problems and have to address each of them to fix your tank as a whole...
1. flow...you have a 1500Lph on a 150L tank which is 9.3x turnover per hour...as I've mentioned before in algae threads...flow = algae....more flow = more algae
some people will recommend 5x turnover..I recommend 2x...even 1x during problems such as these...
flow it's nice and cool to have so it can add some movement to the water...you can achieve the same movement with a 1x turnover and nozzles
something like this
and then your nozzles attached to it and point them at wherever you want to see movement...
filtration doesn't need a 9x turnover in a 39gal tank, use things like filter floss for better water not increased flow
2. co2...I'm assuming you have harder water being from england and using co2 to lower ph...which is a no no...and you also don't have a controller which will make the ph swing up/down all the time...and adjusting it with a bubble counter and checking ph daily doesn't account for lights off. I would not advise anyone to use co2 to correct a swing higher than .5 because it'll just be a waste of co2 and you can't account for lost pressure and you'll have to keep adjusting the bubble counter...trust me on this...get a co2 controller...they go for around 100$ on aliexpress with dual tds/ph controllers and will make your life 10x easier
these swings alone will make your water parameters unpredictable and again...algae likes imbalance
test your water...ph/gh/kh they're interlaced with each other...harder water = higher ph I'm sure you have a way to test ph on the go as you're using co2...
grab a glass of water when you get home from work leave it overnight and check the ph the next day...if it's over .5 of what you're trying to aim for...
then you should definitely think about using a premix with RO/distilled+tap water when doing water changes to lower the hardness/ph to within that .5 range
I do use co2 with a tds/ph controller my water changes are done at 400ppm tds with top-offs in between and the filter floss switched and sponges washed on the sink once it reaches the 400ppm mark
sometimes it's a week...sometimes 2 weeks..sometimes a month...but only when it reaches 400 is when I actually do a water change my water changes are about 15-20%
my last water change was 3 weeks ago and my controller reads 352 right now and needs another top-off which will more than likely drag this water change to more than a month
which makes me very happy as it's less work for me xD
3. liquid ferts...I haven't met one person yet that doesn't overdose ferts in their tanks because x/y/z plant didn't look so good so let's add a little more
guess what? you're feeding the monster! excess nutrients/minerals contributes to algae growth and it's one of the most common reasons alone for algae blooms
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now looking at this as an outsider....you have excess flow which increases flow/oxygen like crazy...co2 to bring ph down from the excess oxygen and more than likely having hard-water
these 2 alone are fighting each-other...then ferts ferts ferts...
my advice? stop focusing on the lights...cheap lights...expensive lights..pink/blue/yellow..who cares...you can go to the dollar store and grab a washroom bulb and it'll do just fine
reduce the flow to a 2x turnover MAX
get a co2 controller to have stable parameters or get rid of the co2...want to adjust water parameters? co2 controller or RO/distilled premixed in a bucket
forget adjusting by eye with bubble counters and daily testing...it just doesn't work no matter how hard you try
----------> stop using liquid ferts <----------------
get root tabs and as you have a heavily planted tank use 1.5tabs for each 10gallons your tank is close to 40gal so start with 6 tabs...if you plants melt a bit add 1 more (once every 2 weeks)
until your plants are doing ok...keep track of how many you've used in total...and in 6 months from the last one you added...use the same amount of tabs
your ferts are now done once every 6 months instead of daily/every other day
now for cleanup crew...and many people will say don't add fish to fix a problem...honestly...I say DO IT because it just simply works
1 amano shrimp for each 10gals which makes 4 total for you...
1 hillstream loach for each 20gal which makes 2 total
and 2 dwarf bristlenose plecos like the the L144
don't expect to add these fish and they'll clean up your tank..they will help for certain but if you don't fix your other problems..don't expect miracles