@burr_and_bloom
Filter coffee only, mostly light roasts, permanently chasing a cup he had in 2019 and cannot reproduce.
Green spot algae, and the counterintuitive fix is phosphate. Low phosphate in the water column is what triggers it, so dosing rather than starving is the move. I add enough of a comprehensive fertiliser to keep phosphate somewhere around 1ppm and the spots stopped appearing on new leaves within a month.
It showing up only on anubias makes sense too. Slow growing plants hold each leaf for a year, so anything that lands on them stays. Fast growers just outgrow it.
In a low tech tank with plants actually growing, not really. The nutrients cause algae myth comes from tanks where the plants were already stalled. Keep the light modest and dose, that combination is stable.
Sour and bitter in the same cup at 40 seconds is the signature of channelling, not of a grind setting. Water is punching a hole through part of the puck and blasting past the rest, so some coffee is scorched and most of it is barely touched. Going finer makes channelling worse, which is exactly what you are seeing.
Order I would fix things in:
Only once the shot runs evenly should you go back to adjusting grind by taste.
Agreed, though I would exhaust the free fixes first. Plenty of entry grinders make acceptable espresso once distribution is under control.
One thing worth checking rather than assuming: if it is slimy and stringy rather than dusty, and it smells faintly swampy, that is cyanobacteria and it behaves completely differently. Diatoms feel gritty and come off in sheets. Yours sounds like diatoms from the description.
If grind size does not change your drawdown, the water is bypassing the coffee bed rather than going through it. Two usual culprits with a conical.
First, the paper is not sealed against the cone, so water runs down the gap. Rinse with enough water to actually stick the filter to the walls and press the seam down before adding coffee.
Second, and more likely from your description, you are pouring high and hard into the middle, which digs a channel straight down. Pour in slow concentric circles from about 4cm above the bed, stop 1cm short of the paper, and keep the water level fairly low rather than filling the cone in one go.
A thin and slightly salty cup is under extraction, which fits both of those.
If you regularly end up with more coffee than you can drink in a month, freezing in single dose portions works well. Small airtight containers, straight from the freezer into the grinder without thawing, and it holds for months. Do not refreeze what you have opened.
The other half of it is not stirring after the steep. Every stir puts settled fines back in suspension.
Used market it is. Anything I should test in person?
Slight disagreement, or at least a caveat. Tabs cover nitrogen, phosphorus and potassium at the roots but the traces still matter, and green spot algae is usually a water column phosphate problem. If you can stretch to a small bottle of all in one liquid at about 15 dollars that also lasts a ten gallon nearly a year at low tech doses, you are covering both for not much more.