diff --git a/lib/index.js b/lib/index.js
index bf57b87..b50f758 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -38,16 +38,6 @@ function assertGoalsPlugin(peer) {
   if (!peer.goals) throw new Error('gc plugin requires ppppp-goals plugin')
 }
 
-/**
- * @param {Config} config
- * @returns {asserts config is ExpectedConfig}
- */
-function assertValidConfig(config) {
-  if (typeof config.gc?.maxLogBytes !== 'number') {
-    throw new Error('gc requires config.gc.maxLogBytes')
-  }
-}
-
 /**
  * @param {{ db: PPPPPDB | null, goals: PPPPPGoal | null }} peer
  * @param {Config} config
@@ -56,12 +46,6 @@ function initGC(peer, config) {
   // Assertions
   assertDBPlugin(peer)
   assertGoalsPlugin(peer)
-  assertValidConfig(config)
-
-  const MAX_LOG_BYTES = config.gc.maxLogBytes
-
-  /** Number of records that match roughly 1% of the max log size */
-  const CHECKPOINT = Math.floor((MAX_LOG_BYTES * 0.01) / 500) // assuming 1 record = 500 bytes
 
   // State
   const debug = makeDebug('ppppp:gc')
@@ -133,10 +117,11 @@ function initGC(peer, config) {
 
   /**
    * @param {number} percentUsed
+   * @param {number} maxLogBytes
    * @param {{ totalBytes: number; }} stats
    */
-  function reportCleanupNeed(percentUsed, stats) {
-    const bytesRemaining = MAX_LOG_BYTES - stats.totalBytes
+  function reportCleanupNeed(percentUsed, maxLogBytes, stats) {
+    const bytesRemaining = maxLogBytes - stats.totalBytes
     const kbRemaining = bytesRemaining >> 10
     const mbRemaining = bytesRemaining >> 20
     const remaining =
@@ -169,21 +154,27 @@ function initGC(peer, config) {
 
   /**
    * Monitor the log size and schedule compaction and/or cleanup.
+   *
+   * @param {number} maxLogBytes
    */
-  function monitorLogSize() {
+  function monitorLogSize(maxLogBytes) {
     assertDBPlugin(peer)
+
+  /** Number of records that match roughly 1% of the max log size */
+  const CHECKPOINT = Math.floor((maxLogBytes * 0.01) / 500) // assuming 1 record = 500 bytes
+
     function checkLogSize() {
       assertDBPlugin(peer)
       peer.db.log.stats((err, stats) => {
         if (err) return
-        const percentUsed = (stats.totalBytes / MAX_LOG_BYTES) * 100
+        const percentUsed = (stats.totalBytes / maxLogBytes) * 100
         const percentDeleted = (stats.deletedBytes / stats.totalBytes) * 100
         const needsCleanup = percentUsed > 80
         const needsCompaction = percentDeleted > 30
 
         // Schedule clean up
         if ((needsCleanup || needsCompaction) && !hasCleanupScheduled) {
-          if (needsCleanup) reportCleanupNeed(percentUsed, stats)
+          if (needsCleanup) reportCleanupNeed(percentUsed, maxLogBytes, stats)
           if (needsCompaction) reportCompactionNeed(percentDeleted, stats)
           hasCleanupScheduled = true
           if (needsCleanup) {
@@ -212,9 +203,15 @@ function initGC(peer, config) {
     checkLogSize()
   }
 
-  function start() {
+  /**
+   * @param {number?} maxLogBytes
+   */
+  function start(maxLogBytes) {
+    const actualMaxLogBytes = maxLogBytes ?? config.gc?.maxLogBytes ?? null
+    // prettier-ignore
+    if (!actualMaxLogBytes) throw new Error('gc plugin requires maxLogBytes via start() argument or config.gc.maxLogBytes')
     if (!stopMonitoringLogSize) {
-      monitorLogSize()
+      monitorLogSize(actualMaxLogBytes)
     }
   }
 
diff --git a/test/dict-ghosts.test.js b/test/dict-ghosts.test.js
index bfd88fb..8995613 100644
--- a/test/dict-ghosts.test.js
+++ b/test/dict-ghosts.test.js
@@ -25,7 +25,6 @@ function isPresent(msg) {
 test('Dict ghosts', async (t) => {
   const alice = createPeer({
     name: 'alice',
-    gc: { maxLogBytes: 100 * 1024 * 1024 },
     dict: { ghostSpan: 2 },
   })
 
diff --git a/test/feed-decay.test.js b/test/feed-decay.test.js
index 6e3d410..d07dca7 100644
--- a/test/feed-decay.test.js
+++ b/test/feed-decay.test.js
@@ -10,7 +10,6 @@ function getTexts(msgs) {
 test('Feed decay', async (t) => {
   const alice = createPeer({
     name: 'alice',
-    gc: { maxLogBytes: 100 * 1024 * 1024 },
   })
 
   await alice.db.loaded()
diff --git a/test/feed-holes.test.js b/test/feed-holes.test.js
index cf30bc6..7fef74c 100644
--- a/test/feed-holes.test.js
+++ b/test/feed-holes.test.js
@@ -10,7 +10,6 @@ function getTexts(msgs) {
 test('Feed holes', async (t) => {
   const alice = createPeer({
     name: 'alice',
-    gc: { maxLogBytes: 100 * 1024 * 1024 },
   })
 
   await alice.db.loaded()
diff --git a/test/orphan-weave.test.js b/test/orphan-weave.test.js
index 489eef1..52ea5b2 100644
--- a/test/orphan-weave.test.js
+++ b/test/orphan-weave.test.js
@@ -14,7 +14,6 @@ function getTexts(msgs) {
 test('Orphan weave msgs', async (t) => {
   const alice = createPeer({
     name: 'alice',
-    gc: { maxLogBytes: 100 * 1024 * 1024 },
   })
 
   await alice.db.loaded()
diff --git a/test/schedule.test.js b/test/schedule.test.js
index b1abcf9..88852be 100644
--- a/test/schedule.test.js
+++ b/test/schedule.test.js
@@ -8,11 +8,7 @@ function getTexts(msgs) {
 }
 
 test('Cleanup is scheduled automatically', async (t) => {
-  const alice = createPeer({
-    name: 'alice',
-    gc: { maxLogBytes: 4 * 1024 }, // 4kB, approximately 8 messages
-  })
-
+  const alice = createPeer({ name: 'alice' })
   await alice.db.loaded()
 
   // Alice creates her own account
@@ -40,9 +36,8 @@ test('Cleanup is scheduled automatically', async (t) => {
   alice.goals.set(postFeedID, 'newest-3')
   assert('alice set a goal for newest-3 of post feed')
 
-  alice.gc.start()
-
-  await p(setTimeout)(3000)
+  alice.gc.start(4 * 1024), // 4kB, approximately 8 messages
+    await p(setTimeout)(3000)
 
   assert.deepEqual(
     getTexts([...alice.db.msgs()]),
@@ -54,11 +49,7 @@ test('Cleanup is scheduled automatically', async (t) => {
 })
 
 test('Compaction is scheduled automatically', async (t) => {
-  const alice = createPeer({
-    name: 'alice',
-    gc: { maxLogBytes: 6 * 1024 }, // 6kB, approximately 12 messages
-  })
-
+  const alice = createPeer({ name: 'alice' })
   await alice.db.loaded()
 
   // Alice creates her own account
@@ -101,7 +92,7 @@ test('Compaction is scheduled automatically', async (t) => {
   alice.goals.set(alice.db.feed.getID(aliceID, 'post3'), 'all')
   alice.goals.set(alice.db.feed.getID(aliceID, 'post4'), 'all')
 
-  alice.gc.start()
+  alice.gc.start(6 * 1024) // 6kB, approximately 12 messages
 
   await p(setTimeout)(3000)