You hold BTC in Zelcore and want ETH. You open the Fusion tab, type the amount, pick a destination address from your own Ethereum account, and a quote appears in about a second. Twenty minutes later the ETH lands. No exchange login, no withdrawal approval, no KYC pop-up. That flow looks like magic, but it is not. It is four centralized instant-swap providers quietly competing for your order, and the quote you accepted has implications worth understanding before the next trade.
Fusion is the in-wallet swap surface you will reach for most often inside Zelcore. It is also the feature most commonly misunderstood. This guide covers what Fusion is, what it is not, how the fixed-vs-floating rate choice changes the trade, how the MoonPay and Guardarian on-ramps plug into the same wallet, and when you should close Fusion and use a DEX instead.
What Fusion actually is
Fusion is a cross-chain instant-swap aggregator built into Zelcore desktop and mobile. When you request a quote, Fusion queries multiple off-chain providers in parallel and shows you the best one. If you accept, the provider generates a single-use deposit address on the source chain. You send the coins. The provider receives, converts, and pays out the destination coin to your Zelcore-controlled address on the target chain.
Throughout the whole flow, Zelcore keeps custody of your private keys. Fusion only forwards quotes and deposit addresses. Your seed never leaves the wallet. That is worth repeating because the swap itself is custodial in the middle: the provider holds your coins for the minutes between your deposit and their payout. You are trusting a centralized counterparty for that window.
Fusion supports hundreds of cross-chain pairs across the UTXO, EVM, and Solana-family chains Zelcore already handles natively. BTC to ETH, LTC to SOL, FLUX to USDT on Tron, and thousands more combinations are one quote away. If Zelcore supports the chain, Fusion can usually route to or from it.
What Fusion is not
This is the part people get wrong. Fusion is not an on-chain DEX aggregator. It is not 1inch, Paraswap, Matcha, or Jupiter. Those tools execute trades against smart-contract liquidity on a single chain, splitting one order across Uniswap, Curve, Balancer, or Raydium to find the best fill. That is called smart-order routing and it is architecturally impossible for Fusion, because Fusion's quote sources are off-chain services, not AMM pools.
The practical difference matters. An on-chain DEX trade is settled by a smart contract and is fully public on a block explorer. A Fusion swap is a private transaction between you and a centralized provider that aggregates its own liquidity from places like Binance and Kraken. The provider can freeze, refund, or request KYC documents mid-flow if its AML heuristics flag the deposit. Before you swap anything, it helps to know what DeFi actually means in the permissionless sense — Fusion is a convenience layer on top of centralized rails, not DeFi.
The four providers behind Fusion
Fusion currently aggregates quotes from four instant-swap services. Each has its own liquidity, pair coverage, and AML posture. You rarely need to pick one manually because Fusion sorts by best output, but knowing the roster helps you read the quote:
- ChangeNOW. No-account instant swaps, advertised at 900M+ pairs. Offers both fixed and floating rate. KYC is only triggered on risk flags rather than by default.
- SimpleSwap. 1,500+ supported assets, no registration required, AML review only on flagged transactions.
- Godex. Markets a no-KYC, fixed-rate-first service with anonymous trades below its internal risk thresholds.
- StealthEX. No-registration swaps in both fixed and floating modes, with AMLBot-based on-demand screening.
All four are centralized off-chain services. They do not charge a visible per-swap fee; they charge a spread — the gap between the market price of the pair and the rate they quote you. That spread is how they earn, and it is the main thing you are comparing when Fusion shows you four lines. Treat the quoted output amount as the source of truth.
Fixed vs floating rate
Every Fusion quote carries one of two modes, and the choice changes what you are actually buying.
Fixed rate locks the quote for roughly 10 minutes. If you send the deposit within that window, you receive exactly the displayed amount — no surprises. The provider eats any price movement during confirmation. You pay for that certainty with a larger spread, typically 1 to 2 percent above the floating quote on the same pair.
Floating rate shows an indicative number at the moment of quote. The final payout is calculated when your deposit confirms on-chain, using the provider's rate at that exact block. You save the fixed-rate premium, but you absorb whatever the price did during confirmation. Most providers apply a tolerance band of roughly plus-or-minus 3 to 5 percent. If the market moves outside that band while your deposit is confirming, you get re-quoted at the worst rate or offered a refund minus network fees.
The heuristic is straightforward:
- Use floating on fast chains where confirmation lands in seconds or a couple of minutes — Solana, Litecoin, Polygon, most EVM L2s. The market rarely moves enough to matter.
- Use fixed on slow chains where confirmation can take 30 to 60 minutes — Bitcoin during fee spikes, Ethereum mainnet during gas surges. The 1-2% premium buys you certainty against exactly the scenarios where floating would hurt.
Network fees are separate from the provider spread. You pay the source-chain fee to broadcast your deposit, and the destination-chain fee is deducted from your payout. If you are hazy on why those fees exist and how they get priced, the primer on how transaction fees actually work is worth ten minutes before large swaps.
Fiat on-ramps: MoonPay and Guardarian
Fusion handles crypto-to-crypto. For fiat-to-crypto, Zelcore integrates two on-ramps that push purchased coins directly into your own Zelcore addresses.
MoonPay is the primary integration. It supports card and bank purchases of BTC, ETH, USDT, and 100+ other assets. MoonPay is a regulated VASP with multiple EU MiCA-era registrations and tiered KYC: email verification is enough for small purchases, government ID is required above a low threshold, and source-of-funds documentation is triggered above roughly 10,000 EUR per year. Availability covers the US (minus a handful of states), the EU, the UK, and most of Latin America.
Guardarian is the secondary on-ramp, registered as a regulated financial-services company in Estonia. It is positioned for SEPA bank transfers and card payments in the EEA and selected non-EU countries, typically with lower fees than card-only flows for European users.
Both also offer off-ramp flows — crypto to fiat — but expect stricter KYC on the sell side. Full identity verification is the norm for any off-ramp above a few hundred euros. If regional availability or fees look off, check whether the other provider covers your country before assuming the feature is broken.
Fusion vs a DEX aggregator: when to use which
Fusion is the right tool roughly half the time. The rest of the time you want to close it and use WalletConnect to pair Zelcore with a DEX aggregator like 1inch, Matcha, or Jupiter. Here is the decision heuristic:
Use Fusion when:
- You are swapping across chains (BTC to ETH, LTC to SOL, FLUX to USDT).
- The source or destination asset is not on a DEX at all — native BTC, native XMR, native FLUX, native DOGE.
- You want a one-click flow without bridging, wrapping, or approving anything.
- You are moving a small-to-medium amount where 1-2% spread is cheaper than the gas plus bridge plus DEX fees you would pay on-chain.
Use an on-chain DEX aggregator via WalletConnect when:
- The trade is same-chain and the assets are ERC-20 to ERC-20 or SPL to SPL with deep AMM liquidity.
- You want fully non-custodial execution with no off-chain counterparty in the middle.
- You are size-sensitive and the DEX route clearly beats the Fusion quote after gas.
- You want the transaction to be publicly verifiable on a block explorer rather than logged by a provider.
There is also a privacy and trust axis worth naming. Fusion providers log IP addresses, deposit addresses, and destination addresses. An on-chain DEX swap is pseudonymous in the same sense as any block-explorer transaction — public, but not tied to an account you created. Meanwhile Fusion trusts four centralized counterparties; a DEX trade trusts only the smart contracts and the RPC endpoint you query it through.
One last thing before you swap anything meaningful: the three primitives every on-chain trade depends on — wallets, gas, and token approvals — are especially load-bearing when you step off Fusion and into a DEX aggregator. Fusion hides all three; a DEX makes you sign each one yourself. That is the real trade-off between the two tools: Fusion is frictionless because you are paying a provider to absorb the complexity. A DEX is cheaper and more transparent because you are doing the work.
