diff --git a/src/datatokens/Datatokens.ts b/src/datatokens/Datatokens.ts
index 861dac66..e27c8213 100644
--- a/src/datatokens/Datatokens.ts
+++ b/src/datatokens/Datatokens.ts
@@ -67,14 +67,14 @@ export class DataTokens {
      * Approve
      * @param {String} dataTokenAddress
      * @param {String} toAddress
-     * @param {Number} amount Number of datatokens, as number. Will be converted to wei
+     * @param {string} amount Number of datatokens, as number. Will be converted to wei
      * @param {String} address
      * @return {Promise<string>} transactionId
      */
     public async approve(
         dataTokenAddress: string,
         spender: string,
-        amount: number,
+        amount: string,
         address: string
     ): Promise<string> {
         const datatoken = new this.web3.eth.Contract(
@@ -83,7 +83,7 @@ export class DataTokens {
             { from: address }
         )
         const trxReceipt = await datatoken.methods
-            .approve(spender, this.web3.utils.toWei(String(amount)))
+            .approve(spender, this.web3.utils.toWei(amount))
             .send()
         return trxReceipt
     }
@@ -92,14 +92,14 @@ export class DataTokens {
      * Mint
      * @param {String} dataTokenAddress
      * @param {String} address
-     * @param {Number} amount Number of datatokens, as number. Will be converted to wei
+     * @param {String} amount Number of datatokens, as number. Will be converted to wei
      * @param {String} toAddress   - only if toAddress is different from the minter
      * @return {Promise<string>} transactionId
      */
     public async mint(
         dataTokenAddress: string,
         address: string,
-        amount: number,
+        amount: string,
         toAddress?: string
     ): Promise<string> {
         const destAddress = toAddress || address
@@ -109,14 +109,14 @@ export class DataTokens {
             { from: address }
         )
         const estGas = await datatoken.methods
-            .mint(destAddress, this.web3.utils.toWei(String(amount)))
+            .mint(destAddress, this.web3.utils.toWei(amount))
             .estimateGas(function (err, estGas) {
                 if (err) console.log('Datatokens: ' + err)
                 return estGas
             })
 
         const trxReceipt = await datatoken.methods
-            .mint(destAddress, this.web3.utils.toWei(String(amount)))
+            .mint(destAddress, this.web3.utils.toWei(amount))
             .send({
                 from: address,
                 gas: estGas + 1,
@@ -130,14 +130,14 @@ export class DataTokens {
      * Transfer as number from address to toAddress
      * @param {String} dataTokenAddress
      * @param {String} toAddress
-     * @param {Number} amount Number of datatokens, as number. Will be converted to wei
+     * @param {String} amount Number of datatokens, as number. Will be converted to wei
      * @param {String} address
      * @return {Promise<string>} transactionId
      */
     public async transfer(
         dataTokenAddress: string,
         toAddress: string,
-        amount: number,
+        amount: string,
         address: string
     ): Promise<string> {
         return this.transferToken(dataTokenAddress, toAddress, amount, address)
@@ -147,17 +147,17 @@ export class DataTokens {
      * Transfer as number from address to toAddress
      * @param {String} dataTokenAddress
      * @param {String} toAddress
-     * @param {Number} amount Number of datatokens, as number. Will be converted to wei
+     * @param {String} amount Number of datatokens, as number. Will be converted to wei
      * @param {String} address
      * @return {Promise<string>} transactionId
      */
     public async transferToken(
         dataTokenAddress: string,
         toAddress: string,
-        amount: number,
+        amount: string,
         address: string
     ): Promise<string> {
-        const weiAmount = this.web3.utils.toWei(String(amount))
+        const weiAmount = this.web3.utils.toWei(amount)
         return this.transferWei(dataTokenAddress, toAddress, weiAmount, address)
     }
 
@@ -165,7 +165,7 @@ export class DataTokens {
      * Transfer in wei from address to toAddress
      * @param {String} dataTokenAddress
      * @param {String} toAddress
-     * @param {Number} amount Number of datatokens, as number. Expressed as wei
+     * @param {String} amount Number of datatokens, as number. Expressed as wei
      * @param {String} address
      * @return {Promise<string>} transactionId
      */
@@ -180,9 +180,7 @@ export class DataTokens {
             dataTokenAddress,
             { from: address }
         )
-        const trxReceipt = await datatoken.methods
-            .transfer(toAddress, String(amount))
-            .send()
+        const trxReceipt = await datatoken.methods.transfer(toAddress, amount).send()
         return trxReceipt
     }
 
@@ -190,14 +188,14 @@ export class DataTokens {
      * Transfer from fromAddress to address  (needs an Approve operation before)
      * @param {String} dataTokenAddress
      * @param {String} fromAddress
-     * @param {Number} amount Number of datatokens, as number. Will be converted to wei
+     * @param {String} amount Number of datatokens, as number. Will be converted to wei
      * @param {String} address
      * @return {Promise<string>} transactionId
      */
     public async transferFrom(
         dataTokenAddress: string,
         fromAddress: string,
-        amount: number,
+        amount: string,
         address: string
     ): Promise<string> {
         const datatoken = new this.web3.eth.Contract(
@@ -206,7 +204,7 @@ export class DataTokens {
             { from: address }
         )
         const trxReceipt = await datatoken.methods
-            .transferFrom(fromAddress, address, this.web3.utils.toWei(String(amount)))
+            .transferFrom(fromAddress, address, this.web3.utils.toWei(amount))
             .send()
         return trxReceipt
     }
@@ -215,9 +213,9 @@ export class DataTokens {
      * Get Address Balance for datatoken
      * @param {String} dataTokenAddress
      * @param {String} address
-     * @return {Promise<number>} balance  Number of datatokens, as number. Will be converted from wei
+     * @return {Promise<String>} balance  Number of datatokens. Will be converted from wei
      */
-    public async balance(dataTokenAddress: string, address: string): Promise<number> {
+    public async balance(dataTokenAddress: string, address: string): Promise<string> {
         const datatoken = new this.web3.eth.Contract(
             this.datatokensABI,
             dataTokenAddress,
@@ -307,19 +305,19 @@ export class DataTokens {
         return this.web3.utils.fromWei(trxReceipt)
     }
 
-    /** Convert from number to wei
-     * @param {Number} amount
-     * @return {Promise<string>} string
-     */
-    public toWei(amount) {
-        return this.web3.utils.toWei(String(amount))
-    }
-
-    /** Convert from wei to number
+    /** Convert to wei
      * @param {String} amount
      * @return {Promise<string>} string
      */
-    public fromWei(amount) {
+    public toWei(amount: string) {
+        return this.web3.utils.toWei(amount)
+    }
+
+    /** Convert from wei
+     * @param {String} amount
+     * @return {Promise<string>} string
+     */
+    public fromWei(amount: string) {
         return this.web3.utils.fromWei(amount)
     }
 }
diff --git a/test/integration/ComputeFlow.test.ts b/test/integration/ComputeFlow.test.ts
index 4b43a6e8..cba228de 100644
--- a/test/integration/ComputeFlow.test.ts
+++ b/test/integration/ComputeFlow.test.ts
@@ -42,8 +42,8 @@ describe('Compute flow', () => {
 
     const dateCreated = new Date(Date.now()).toISOString().split('.')[0] + 'Z' // remove milliseconds
 
-    const marketplaceAllowance = 20
-    const tokenAmount = 100
+    const marketplaceAllowance = '20'
+    const tokenAmount = '100'
 
     const timeout = 86400
     const algorithmMeta = {
@@ -114,7 +114,7 @@ describe('Compute flow', () => {
         })
 
         it('Alice publishes dataset with a compute service that allows Raw Algo', async () => {
-            price = datatoken.toWei(2) // in datatoken
+            price = datatoken.toWei('2') // in datatoken
             cluster = ocean.compute.createClusterAttributes(
                 'Kubernetes',
                 'http://10.0.0.17/xxx'
@@ -261,7 +261,7 @@ describe('Compute flow', () => {
         })
 
         it('Bob gets datatokens from Alice to be able to try the compute service', async () => {
-            const dTamount = 20
+            const dTamount = '20'
             await datatoken
                 .transfer(tokenAddress, bob.getId(), dTamount, alice.getId())
                 .then(async () => {
@@ -284,7 +284,7 @@ describe('Compute flow', () => {
             const tx = await datatoken.transferWei(
                 computeOrder['dataToken'],
                 computeOrder['to'],
-                computeOrder['numTokens'],
+                String(computeOrder['numTokens']),
                 computeOrder['from']
             )
             const response = await ocean.compute.start(
@@ -352,7 +352,7 @@ describe('Compute flow', () => {
             const algoTx = await datatoken.transferWei(
                 algoOrder['dataToken'],
                 algoOrder['to'],
-                algoOrder['numTokens'],
+                String(algoOrder['numTokens']),
                 algoOrder['from']
             )
             const order = await ocean.compute.order(
@@ -367,7 +367,7 @@ describe('Compute flow', () => {
             const tx = await datatoken.transferWei(
                 computeOrder['dataToken'],
                 computeOrder['to'],
-                computeOrder['numTokens'],
+                String(computeOrder['numTokens']),
                 computeOrder['from']
             )
             const response = await ocean.compute.start(
diff --git a/test/integration/Marketplaceflow.test.ts b/test/integration/Marketplaceflow.test.ts
index db16ddc9..cb0bf480 100644
--- a/test/integration/Marketplaceflow.test.ts
+++ b/test/integration/Marketplaceflow.test.ts
@@ -26,8 +26,8 @@ describe('Marketplace flow', () => {
     let data
     let blob
 
-    const marketplaceAllowance = 20
-    const tokenAmount = 100
+    const marketplaceAllowance = '20'
+    const tokenAmount = '100'
 
     describe('#MarketplaceDownloadFlow-Test', () => {
         it('Initialize Ocean contracts v3', async () => {
@@ -84,7 +84,7 @@ describe('Marketplace flow', () => {
         })
 
         it('Alice publishes a dataset', async () => {
-            price = datatoken.toWei(10) // in datatoken
+            price = datatoken.toWei('10') // in datatoken
             const publishedDate = new Date(Date.now()).toISOString().split('.')[0] + 'Z'
             const timeout = 0
             service1 = await ocean.assets.createAccessServiceAttributes(
@@ -146,11 +146,11 @@ describe('Marketplace flow', () => {
         it('Marketplace posts asset for sale', async () => {
             accessService = await ocean.assets.getServiceByType(ddo.id, 'access')
             price = 20
-            assert(accessService.attributes.main.cost * price === datatoken.toWei(200))
+            assert(accessService.attributes.main.cost * price === datatoken.toWei('200'))
         })
 
         it('Bob gets datatokens', async () => {
-            const dTamount = 20
+            const dTamount = '20'
             await datatoken
                 .transfer(tokenAddress, bob.getId(), dTamount, alice.getId())
                 .then(async () => {
@@ -167,7 +167,7 @@ describe('Marketplace flow', () => {
                     return await datatoken.transferWei(
                         res['dataToken'],
                         res['to'],
-                        res['numTokens'],
+                        String(res['numTokens']),
                         res['from']
                     )
                 })
diff --git a/test/integration/Simpleflow.test.ts b/test/integration/Simpleflow.test.ts
index 7bc6129f..8d10cfe5 100644
--- a/test/integration/Simpleflow.test.ts
+++ b/test/integration/Simpleflow.test.ts
@@ -16,8 +16,8 @@ describe('Simple flow', () => {
     let datatoken
     let tokenAddress
     let transactionId
-    const tokenAmount = 100
-    const transferAmount = 1
+    const tokenAmount = '100'
+    const transferAmount = '1'
     const blob = 'http://localhost:8030/api/v1/services/consume'
     describe('#test', () => {
         it('Initialize Ocean contracts v3', async () => {