diff --git a/frontend/src/lib/components/workspaceSettings/CustomInstanceDbSelect.svelte b/frontend/src/lib/components/workspaceSettings/CustomInstanceDbSelect.svelte
index a00377f683..ba7e006132 100644
--- a/frontend/src/lib/components/workspaceSettings/CustomInstanceDbSelect.svelte
+++ b/frontend/src/lib/components/workspaceSettings/CustomInstanceDbSelect.svelte
@@ -33,6 +33,15 @@
 	let openedDbNameWizard = $state(false)
 
 	let status = $derived(customInstanceDbs.current?.[value ?? ''])
+
+	let onlySelectedTags = $derived(
+		safeSelectItems(
+			Object.entries(customInstanceDbs.current ?? {})
+				.filter(([_, db]) => !tag || db.tag === tag)
+				.map(([name, _]) => name)
+		)
+	)
+	let currentIsAlreadyUsedElsewhere = $derived(tag && status && status.tag !== tag)
 </script>
 
 <div class="flex relative items-center {className}">
@@ -42,20 +51,23 @@
 		bind:value
 		onCreateItem={(i) => (value = i)}
 		placeholder="PostgreSQL database name"
-		items={safeSelectItems(Object.keys(customInstanceDbs.current ?? {}))}
+		items={onlySelectedTags}
 		disabled={!$isCustomInstanceDbEnabled}
 	/>
 
 	<Button
 		spacingSize="xs2"
 		variant="default"
-		wrapperClasses={'absolute right-1.5 h-6'}
+		wrapperClasses={'absolute right-1.5 h-6 bg-surface-input'}
 		onClick={() => (openedDbNameWizard = true)}
+		disabled={currentIsAlreadyUsedElsewhere}
 	>
 		{#if !status}
 			<span class="text-yellow-600 dark:text-yellow-400">
 				Setup <ArrowRight class="inline" size={14} />
 			</span>
+		{:else if currentIsAlreadyUsedElsewhere}
+			<span class="text-red-400 flex gap-1">Used as {tag}</span>
 		{:else if !status.success}
 			<span class="text-red-400 flex gap-1">
 				Error <TriangleAlert class="inline" size={16} />
@@ -73,10 +85,7 @@
 	{tag}
 	bottomHint={wizardBottomHint}
 	bind:opened={
-		() =>
-			openedDbNameWizard
-				? { dbname: value ?? '', status: customInstanceDbs.current?.[value ?? ''] }
-				: undefined,
+		() => (openedDbNameWizard ? { dbname: value ?? '', status: status! } : undefined),
 		(v) => !v && (openedDbNameWizard = false)
 	}
 />
diff --git a/frontend/src/lib/components/workspaceSettings/DucklakeSettings.svelte b/frontend/src/lib/components/workspaceSettings/DucklakeSettings.svelte
index b728f1ab3c..c1f6d7a4ce 100644
--- a/frontend/src/lib/components/workspaceSettings/DucklakeSettings.svelte
+++ b/frontend/src/lib/components/workspaceSettings/DucklakeSettings.svelte
@@ -72,7 +72,7 @@
 	import Tooltip from '../Tooltip.svelte'
 	import ConfirmationModal from '../common/confirmationModal/ConfirmationModal.svelte'
 	import { createAsyncConfirmationModal } from '../common/confirmationModal/asyncConfirmationModal.svelte'
-	import { clone, filterObject } from '$lib/utils'
+	import { clone } from '$lib/utils'
 	import Alert from '../common/alert/Alert.svelte'
 	import { deepEqual } from 'fast-equals'
 	import Popover from '../meltComponents/Popover.svelte'
@@ -125,9 +125,7 @@
 		)
 	)
 
-	const customInstanceDbs = resource([], async () =>
-		filterObject(await SettingService.getCustomInstanceDbs(), (_, v) => v.tag === 'ducklake')
-	)
+	const customInstanceDbs = resource([], SettingService.getCustomInstanceDbs)
 
 	async function onSave() {
 		try {
diff --git a/frontend/src/lib/utils.ts b/frontend/src/lib/utils.ts
index fe59716071..b0a40bc44a 100644
--- a/frontend/src/lib/utils.ts
+++ b/frontend/src/lib/utils.ts
@@ -1655,12 +1655,3 @@ export function getCssColor(
 }
 
 export type IconType = Component<{ size?: number }> | typeof import('lucide-svelte').Dot
-
-export function filterObject<Key extends string, Value>(
-	obj: Record<Key, Value>,
-	f: (k: Key, v: Value) => boolean
-): Record<Key, Value> {
-	return Object.fromEntries(
-		Object.entries(obj).filter(([k, v]) => f(k as Key, v as Value))
-	) as Record<Key, Value>
-}