well, this is what it comes with from the factory, and if the 2028 is like my 2444, it came with just enough to fill the trays perfectly.
1 x Eheim Install Set 1, 0.65in (Suction)
1 x Eheim Install Set 2, 0.65in (Pressure)
1 x EHFIMECH (Hollow Ceramic Rings) 1L
2 x Eheim SUBSTRAT Pro 2L
So, that would mean it will hold 3 litres of media total
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