Ionic tabs icon not showing

Question

I can't show my feed tab icon:

myapp/src/app/tabs/tabs.page.html

<ion-tab-button tab="tab1">
  <ion-icon name="triangle"></ion-icon>
  <ion-label>Tab 1</ion-label>
</ion-tab-button>

<ion-tab-button tab="tab2">
  <ion-icon name="ellipse"></ion-icon>
  <ion-label>Tab 2</ion-label>
</ion-tab-button>

<ion-tab-button tab="tab3">
  <ion-icon name="square"></ion-icon>
  <ion-label>Tab 3</ion-label>
</ion-tab-button>

<ion-tab-button tab="feed">
   <ion-icon ios="ios-alert" md="md-alert"></ion-icon>
  <ion-label>Feed</ion-label>
</ion-tab-button>

But if i try square, ellipse or triangle like the others tabs work:

myapp/src/app/tabs/tabs.page.html

<ion-tab-button tab="tab1">
  <ion-icon name="triangle"></ion-icon>
  <ion-label>Tab 1</ion-label>
</ion-tab-button>

<ion-tab-button tab="tab2">
  <ion-icon name="ellipse"></ion-icon>
  <ion-label>Tab 2</ion-label>
</ion-tab-button>

<ion-tab-button tab="tab3">
  <ion-icon name="square"></ion-icon>
  <ion-label>Tab 3</ion-label>
</ion-tab-button>

<ion-tab-button tab="feed">
  <ion-icon name="triangle"></ion-icon>
  <ion-label>Feed</ion-label>
</ion-tab-button>

My github project

Answer 1

in ionic 5 md and ios not working.use this icon

 <ion-icon name="alert-circle-outline"></ion-icon>

and for future Reference it's official ionic 5 doc here

https://ionicframework.com/blog/announcing-ionic-5/