I've had my \~65-gallon (250 Liters net) tank for 3 years. Everything was going great, despite a few minor hiccups over the years, I managed to grow stunning plants with extremely red Rotalas, all without any liquid fertilization.

Then, I moved 4 months ago. I did a complete substrate change. I used to have an inert substrate with Dennerle NutriBasis 6in1 underneath, which was probably depleted by then. I figured I might as well change everything and get a finer sand for my Corydoras. So I bought extra-fine aquarium sand and put fresh Dennerle 6in1 underneath, just like before.

I replanted my old plants, but algae started to appear. I started liquid fertilization around the same time, and I think that was the trigger. For the past 3 months, I've been constantly fighting it and can't seem to fix the issues. Today, I have hair/filamentous algae on my plants and glass, oedogonium/green fuzz, and Black Beard Algae (BBA) on my equipment, my Nerite snail, and a few plants. I spend my time trimming and cleaning, but the algae always comes back.

Initially, I was dosing 7ml of 2Hr Aquarist APT 3 (Complete) daily, as recommended on their website. But I realized my phosphates were skyrocketing while my nitrates weren't increasing at all. For the last 3 weeks, I've reduced my dosing to only 2ml of APT 3 daily.

Regarding CO2, I have to run about 8 bubbles per second. My drop checker is blue/green at 1:00 PM (when lights turn on), and then stays light green for the rest of the day until the CO2 shuts off.

Over the last 3 weeks, my parameters were fluctuating around this range:

* pH: 6.6 to 7.2
* NO3: 2 to 4 ppm
* PO4: 0.2 to 0.4 ppm
* KH: 6
* GH: 7

But today's test was disastrous, even though I haven't changed my routine at all:

* pH: 6.2
* NO3: 2 ppm
* PO4: 0.4 ppm
* KH: 6
* GH: 5

I don't even know why my GH is suddenly lower than my KH, or why my pH dropped so low.

Here is my full setup:

Equipment:

* Filter: JBL e1502
* Light: Chihiros A2 MAX
* CO2: 10kg bottle with Chihiros Inline Diffuser
* Drop Checker: Eheim liquid
* Fertilizer: 2Hr Aquarist APT 3
* Test Kit: JBL Liquid test kit

Schedule:

* Light: 1:00 PM to 8:00 PM (currently at 50% intensity. I was at 70% before I moved, but I reduced the intensity when the algae came)
* CO2: 11:00 AM to 7:30 PM

Fishs:

* 3x Flame Tetras
* 8x Nannostomus beckfordi
* 4x Inpaichthys kerri (Blue Emperor)
* 3x Cardinal Tetras
* 8x Otocinclus
* 8x Corydoras julii
* 2x Pearl Gouramis (Couple)
* 2x Apistogramma macmasteri (Couple)
* 1x Bristlenose Pleco (Ancistrus)
* 1x L471 Pleco

Plants:

* Rotala Red
* Cryptocoryne
* Echinodorus
* Limnophila sessiliflora
* Nymphaea Lotus
* Alternanthera reineckii 'Rosanervig' & 'Lila'
* Crinum calamistratum
* Anubias barteri var. nana 'Golden'
* Bucephalandra 'Malawi Pink'
* Hygrophila polysperma 'Rosanervig'

If anyone has any advice on how to get out of this nightmare, I would be forever grateful. Here is a photo from a month ago, just after a heavy trim and a small water change. The others photo was just before, to show the algae

I am desperate... 3 months fighting an endless algae outbreak after a move.