Can I resolve the krogan / salarian conflict with both sides supporting the Alliance?
Yes you can
To do so, You have to cure the Genophage, and then save the salarian councillor. (Captain Kirrahe or Thane must be alive)
You can also gain both their support under specific circumstances.
- Wreave must be alive instead of Wrex.
- You had to destroy Maelon's data in ME2.
With Maelon's data destroyed Eve dies during the run towards the genophage distribution facility, you can then persuade Mordin that with Eve dead Wreave will have no one to control his krogan behavior and he will agree on faking the genophage cure. Wreave thinks he's cured, you get Krogan support. You didn't cure the genophage, you get Salarian support.
If Wrex is alive, the only way is by saving the council dude.
Either way is pretty heartbreaking, You either lose Wrex or you lose Thane or Kirrahe.
spoilers
this is the total number of war assets from the Salarians:
125 from saving the Salarian councilor in me1
35 for letting Kirahee die and talking to Lt. Tolen at the STG base in me3
25 from Mordin if you persuade him that curing the genophage is a bad
idea with Wreav in charge and Eve dead
150 from sabotaging the cure and
8 from a Salarian side mission
= 343
You also get the Krogan too with this
25 from Wreav
25 from Grunt if he survived me2 and his loyalty mission was completed
50 from Arlak company
50 from n7 Cerberus attack
345 from Krogan clans and also speaking with Diana Allers
40 from Krogan side mission
300 Clan Urdnot
=795
Add them together and you get a total war asset amount of 1138.
When you cure the genophage and lose the extra Salarian support, you get 875+169 which equals to 1044.
So kill Wrex and destroy Maelon's data. All it will do is change dialog, nothing bad.