hiimstring3 :
Thanks you very much. I am only wondering, if one the the ink things in the ink system is empty, but there is still ink in the others, will I have to replace the whole thing or can I remove a cartridge and replace it with a full one?
If your talking about the ink system I posted a link to, all you do is refill the external tanks with ink that's formulated for your printer like this ink here:
http://www.inkxpro.com/Claria-4-color-hi-definition-ink-for-epson-printer-p/ink-epson-4-color-dye-ink.htm or here
http://www.inksupply.com/printer_products.cfm/p/Epson_WorkForce_WF-3540.html
The ink tanks with the 1st system I linked to all have 100ml (about 3.5oz) of ink in them already which is about equivalent to 7-10 Epson cartridges or 28-40 Epson cartridges for all colors. So it will be quite a while before you have to add ink.
If you don't like having the separate external tanks you can always get refillable cartridges. These are easier to set up but not quite as easy in the long run as having the separate external tanks.
The easiest way to save on ink is to just buy Aftermarket cartridges that are already filled, you wont save as much but, you will still save quite a bit.
Here's the epson OEM ink :
http://www.epson.com/cgi-bin/Store/jsp/BuyInkResultsA.do?sku=C11CC31201&type=1&BV_UseBVCookie=yes
And here are some Aftermarket cartridges:
http://www.123inkjets.com/Epson/Ink-Cartridge/WorkForce/WF-3540/8033-Printer.html http://www.imarketcity.com/ept1se3.html http://www.imarketcity.com/ept1se2.html
Either way you can save allot!
P.S. Take note of edit on the bottom of the first post.