my bad, this is the garden path. this would be akin to having a tank area that is lit up with lights and leafy plants in the water. harvesting them as they grow. except this way your encouraging any form of algae that wants to be there under the conditions.
there are a heap of these kinds. you might have just got unlucky in the algae lotto but i doubt it. your feed inputs would be higher than what most others use this SM thing for.
different colour algae will have different life stage sizes and time lengths etc.
lets say you built a thin glass tank and plumbed to it but had it near your window facing the sun light. you have added another algae scrubber system.
ive had a quick look through your post. good work, your rather thorough.
i beg to differ that it is not working though. maybe your feed load is just too much for it to handle completely. consider working out a way to catch the fish waste when it is a solid and remove it. that will also ease the load.
this is done with tapered tanks and a ball tap off valve. you flush out a few litres every couple of days. that will stop the need for a lot of algae area.
it didn't seem to me that your tap water was high in silicates. stop using the chemical fixes. the only need for adding fertiliser is if one of the elements is lacking and limiting the growth, called a limiting factor. that would result in there being nutrient, like phosphate being present and not being used. obviously not the case with this good growth and water tests. having said that you can have a situation where growth occurs, then it stops, until an element is present again. i must say, its really good that you went to get the tests done.
go read some about filamentous algae. i think you will find that part of its life cycle does not involve them being in longer strands. ie they can be very small. adult may be strands..and its growing and thriving, doing its full cycle.
even so, all you need to do is to get a microscope ( borrow) and identify the algae kind and then check its life cycle to find out if i am correct.
you can even get an idea of the size of the algae under the scope. obviously your sock filter is too coarse to filter the smaller particles out. what is it 150 microns?
i have had them at 10 and 5 and 1 micron.
using these fine filters is not the best fix because it may be required all the time.
like if you leave them to almost block they could filter finer than their rating but overflow is probable too. so its a lot of work using these.
though i have not checked how long you left this run without playing with things like chemicals and salt. so i dont know if you have let it become stable to see if time will ease it. you could have been playing up with it too much.. anyway, this is how we learn things.
your fix on the source water holding so much phosphate should be using rain water.
it does make me wonder if there are farms throwing round ferts where your town water storage is, but also look at it like this.
you are also throwing fertlisers in your tank everytime you feed.
on top of the tap water which already has high phosphate.
so if you want to continue feeding like this you need to upsize something to deal with it. also get a thousand litre (or more) water storage tank and catch the rain off the roof but give the settlement area a go.
- I don't know why...