To finish my long, boring, rambling story that actually does have a point, I swear it does:
In the end I started ordering 3 different sizes of Tropican pellets: I get the "Cockatiel" size for my Cockatiel, the "Conure" size for my Green Cheek and my Quaker, and then for my Senegal, who HAS TO hold each individual pellet as he eats them, I had to get an even larger size, so I got the next size up, which is the "African Gray" size...They also have one larger size for "Macaws and Cockatoos" that are huge. But my Senegal is good with the "African Gray" size...So every month I order 4 different bags of Tropican Pellets, 1 bag of Cockatiel, 2 bags of Conure, and 1 bag of African Gray. And they absolutely LOVE THEM. Even my Cockatiel, who is picky as all-hell, now eats her pellets every day...And to make things even better/easier/cheaper, I also switched to their Tropimix seed-mix, because not only is it basically exactly the same as the Higgins California Blend seed-mix, even looks exactly the same, the Tropimix seed-mix also contains some Tropican pellets! So even when they are eating their 1/4 cup of healthy,
low-fat, sunflower seed/nut/dried corn free seed-mix, they are also getting more Tropican pellets in their seed-mix! And that's why I really love the Tropican pellets/Tropimix seed-mix daily diet, because it's healthy, it's low-fat, it's low-sugar (the Tropican pellets are sweetened only with natural fruit-juice not-from-concentrate), the Tropimix seed-mix is extremely varied and contains many, many different types of seeds, grains, legumes, dried herbs, dried veggies, etc., AND because even if they leave some of their Tropican pellets for the day, they still eat all of their Tropimix seed-mix every day, which also contains Tropican pellets, so they're getting more pellets every day anyway! And I don't think they know it, which is smart, they think they're eating a seed/grain/veggie mix but they are actually getting the same pellets in it that are in their pellet-bowl. And the Tropican pellets smell exactly like JuicyFruit gum! Yes, I've eaten them, I always try everything that I feed my birds, and they are pretty good! Much tastier than the Zupreem Natural or Fruit pellets!
***So, main point of my rambling here is that if your Cockatiels are currently "Seed-Addicts", that's okay, they are adult Cockatiels that are weaned and they are much better-off eating a seed-mix meant for adults than being fed hand-feeding formula meant for baby birds...Not only is the hand-feeding formula too high in calories, fat, carbs, and way too nutrient-dense for an adult bird, but it also encourages hormonal behavior for a number of different reasons, first because it's warm and mushy and all warm, mushy foods encourage hormonal behavior because it is what they were fed as babies, but the fact that it is actually baby bird hand-feeding formula also often causes some regression in adult birds and they start displaying typical baby-bird behaviors if they are fed it with a syringe on a continual basis (tube/Crop feeding them handfeeding formula with a crop-needle is different, it doesn't elicit a "feeding-response" and they do not actively participate in the process when they are tube/crop fed with a crop-needle)...So if your adult Cockatiels absolutely refuse to eat Zupreem pellets, obviously there are other pellets you can try, but more importantly is to first stop feeding them hand-feeding formula meant for rapidly developing, growing baby birds,
as they are much better-off eating a seed-mix meant for adult birds; and just because they are eating a seed-mix as their daily staple diet doesn't mean that it has to be a "bad" thing at all, you just have to choose a healthy, quality, low-fat seed-mix that contains no sunflower seeds, no peanuts/nuts of any kind, and no dried/cracked corn,
but rather is a varied-mix of lower-fat seeds, grains, legumes, herbs, veggies, fruit, etc. And once you make that switch and get them eating a healthy seed-mix meant for adult birds and are no-longer feeding them any kind of formula daily, THEN you don't have to rush with transitioning them onto a pellet staple, you can take your time and find a pellet brand/type that they like. If they don't like Zupreem then that's actually not a bad thing, because as someone who fed Zupreem Natural for over a year to her own birds I can tell you that it's not that great a pellet...not horrible by any means, but not great. I'm an extremely pleased with the Tropican pellets and the Tropimix seed-mix daily diet combo, and if the Avian Vets at the University of Pennsylvania School of Veterinary Medicine recommend Tropican/Tropimix to their clients and feed it to their own parrots, then that's good enough for me...Worth a try....
***By the way, the Tropican pellets in any Petco store are sold in 2-pound bags for $9.99, but on Chewy.com they are only $7.99 a bag...I go through one bag a month for each bird basically, so I order 4 bags a month...But keep in-mind that I'm also feeding Tropimix seed-mix too, if I didn't I'd go through 2 bag of the Tropican pellets per bird per month...But again, the Tropimix seed-mix contains Tropican pellets, so it's really a two-for-one kind of deal. In a Petco store, a 2 pound bag of Tropimix seed-mix costs around $7, but on Chewy.com they cost $5! (that's the "Cockatiel" size of Tropimix, which is absolutely the size you would want to try for your guys)...
***What I would suggest you do is to NOT BUY ANY TROPICAN PELLETS, but rather just buy a bag of the "Cockatiel" size Tropimix seed-mix first. That way you would be able to see if they like either the Tropimix seed-mix and/or the Tropican pellets since they are also included in the Tropimix...You can't lose, spend $5 on Chewy.com or $7 inside any Petco, if they hate it you're only losing at most $7, but if they like it then you've just solved your dietary/bird-food issues completely! Then you could order the Tropican pellets if you wanted to, OR what my CAV told me a lot of people are doing, since he recommends that all his clients feed pellets as their staple but also that they get a small amount of a healthy seed-mix each day too, is they are just feeding them the Tropimix seed-mix as their daily staple and that's it, no separate bowl of only-pellets, because that way they are getting both the pellets and the healthy seed-mix at one time. I am actually thinking of doing this as well, it makes sense, there are quite a lot of the Tropican pellets in the Tropimix seed-mix, it makes sense and it's a lot easier, cheaper, etc...And then I'll literally be able to feed 4 parrots both a healthy pellet and a healthy seed-mix for under $40 a month...