I have a WF-7720 with aftermarket cartridges that I use extensively. Interestingly, the WF-7710 and WF-7720 both use Durabrite pigment inks, whereas the EcoTank version of the 7720, the ET-16500, uses dye inks. I don't know the full reason for this - Epson doesn't draw attention to this. Perhaps because dye inks are cheaper to manufacture and they want higher margin on the stuff they are giving away by the bottle. Pigment inks have micro particles in suspension, so it may be for clogging reason on the EcoTank version. I personally suspect it's mostly because Epson likes to carefully manage features in the EcoTank printers - for example the ET-16500 doesn't do borderless printing, even though the WF-7720 does great borderless and they are the exact same engine. But it may also be because dye is slightly less viscous and the 16500 is basically a manufacturer-supplied continuous ink system bolted onto the side of a WF-7720, and it has a longer ink path and requires more suction to pull through.
I always try to match the characteristics of the original ink as much as I can when I use aftermarket. As I said above, I don't know the exact reason Epson went with dye with the 16500, but I would not want to use Epson's dye inks in a 7710/7720 unless I were using a full CISS. The other reason you don't want to use dye inks is that your 7710's printer driver will be optimized for dealing with pigment black versus dye black for photo printing, which requires the driver to make different ink decisions. It won't make the right decisions for dye inks, your 7710 driver will be making ink decisions based on pigment inks. With my own refillable cartridges, I use entirely pigment inks.
I mostly use pigment ink from Inksupply.ca, which is a Canadian supplier of Inkowl.com inks. Inkowl is professional, and I recommend them. Their inks are good, and do not break the bank terribly. I find the original Epson inks are very blue-heavy and Inkowl's ink is actually a little bit better on that front. I say I mostly use their ink, because I have occasionally used some Chinese inks. In fact, for black I mostly use a big ole bottle of Chinese black pigment ink. I wouldn't recommend going to Chinese inks directly through Ali Express - the vendors there take fleecing you to an art form. Some are reliable, most are just so desperate for a buck they will say whatever it is they think you want to hear. You will have a lot of hit and miss there, and you will wade through a lot of cruft before you find the good vendors. My Chinese ink I sourced through inksupply.ca -
this is the black ink I still use, and
this is the colour set I occasionally use.
Now, as far as printer clogging goes, I found that I could not just put ink into my WF-7720's T252 refillable cartridges and just use them. I had terrible clogging issues, or issues where a page would print and then it would start to fade out. No end of troubles. I discovered that the aftermarket cartridges need to have the ink drawn through to eliminate all air bubbles in the draw line, to get air flowing into the air return line, and to generally eliminate stickiness in the valves and make sure the internal ink filter is properly wetted. Otherwise it gets vapour locked. Not many ink suppliers tell you this, they say just keep hitting clean up to ten times or more. That can work if you are persistent enough, but it's hard on the printer and as the cartridges start to flow, they all won't flow at the same time and those that do will dump a ton of ink into your cleaning pads. I had to find out through experimentation what to do. I put a syringe up into the bottom cartridge port and draw some ink through. Just the plastic nib on the syringe, not a needle tip. If it's a clean syringe you can carefully replace the ink back into the cartridge from the top. It can be hard to get the nib alone on syringes far enough up the bottom port to activate the valve that's there, so special syringe tips are your friend here. Something like
these from Ali Express. Once you do this for a set of cartridges, if you refill them before they run all the way dry then you don't need to do it again. If you do run a cartridge right dry, then you will need to do this again to eliminate all air from the feed.
