I use Epson 220ml carts emptied into bottles to top up the system.
That is a good strategy!
Next time I'm buying either the replacement for the 3800 or the 7900 and will never use third party inks again.
Even the 3800 carts are a bit small. The larger carts are great.
I have been able to find Epson inks cheaper than the 3rd party pigment inks (which run $100 to $180 per liter.)
You also have to be very careful with the 3rd party inks about their gamut claims. I looked at many that claimed to be as good as the Epson 7800 K3 inks. Most were **worse** than the Epson 7600 K2 inks, including the most expensive ones like the Pantone (far worse than the 7600 K2 at low "L" values if I remember correctly.)
I did successfully use some 3rd party "Claria match" (quote unquote ) dye inks for proofing only. At $27 per liter they werre very economical and had good gamut.
But, I **never** used them for final prints, only for large proofs (24x36, etc.) I just could not count on the longevity. No 3rd party manufacturer really has good longevity data that they publish out and stand behind! Just vague claims.
Best,
Michael