Goldfish Testing Your Decks

Learn how to use Icarian’s goldfish simulator to test your Commander deck’s consistency and performance.

What Is Goldfishing?

Goldfishing is playing Magic “against no opponent” to test your deck:

• Draw opening hands
• Simulate turns
• Test mana curve
• Check consistency
• Identify problems

It’s called “goldfishing” because a goldfish doesn’t interact - you’re just testing your own deck.

Why Goldfish Test?

Goldfish testing helps you:

1. Test mana curve - See if you can cast spells on curve
2. Evaluate land count - Determine if you have enough/too many lands
3. Find dead hands - Identify problematic opening hands
4. Test ramp - See how quickly you can play your commander
5. Spot clunky draws - Find turns where you have nothing to play

Starting a Goldfish Session

To goldfish your deck:

1. Open your deck
2. Open Goldfish from the deck’s menu
3. Click Draw a hand: Icarian shuffles your deck (the commander stays in the command zone) and draws 7 cards
4. Review the hand
5. Keep it with Next turn, or Mulligan

The Opening Hand

Your opening hand is 7 random cards from your deck; your commander stays in the command zone. The session’s stats show the hand’s land count and average mana value.

Decide whether to keep or mulligan based on: - Land count (typically want 2-4 lands) - Castable spells - Early game plays - Curve of the hand

Mulligans (London Mulligan)

If you don’t like your hand:

1. Click Mulligan (only before your first turn)
2. All 7 cards go back and you draw 7 new cards
3. Your first mulligan in Commander is free: you keep all 7
4. Each mulligan after that puts one more card on the bottom of your library, highest mana value first

Example: - First mulligan: Draw 7, keep 7 (free) - Second mulligan: Draw 7, put 1 on bottom (6 card hand) - Third mulligan: Draw 7, put 2 on bottom (5 card hand)

Icarian counts the mulligans you take (the Mulligans stat).

Simulating Turns

After keeping your opening hand:

1. Click Next turn
2. Draw a card for the turn
3. See updated hand
4. Review what you can play
5. Continue clicking Next turn to progress, and End session when you’re done

Each turn, Goldfish plays a land, then casts your commander if any order of the rocks, dorks and land ramp in hand lets it pay for it this turn, along with whatever ramp still fits. Otherwise it casts as many rocks, dorks and land ramp spells as your mana allows, in the order that leaves the most mana for next turn (so a turn-2 Sol Ring pays for an Arcane Signet after it). It pays with lands and rocks of the right colors. On the battlefield, every card that paid for something this turn turns sideways, the way you’d tap it at a table, and everything straightens up when the next turn begins. Each copy of a card taps on its own.

Which land it plays: with more than one land in hand, Goldfish plays the one that lets it cast your commander, or else spend the most mana this turn. When they’re equal, it plays the land that’s worst to hold: one that enters tapped anyway, then a fastland while it still enters untapped, then one adding a color your commander or hand needs. A spell that’s also a land (like Emeria’s Call) is played as a land only when you have no other land in hand.

Lands that enter tapped: a tapland comes in sideways and makes no mana that turn. Lands that enter tapped unless something is true (check lands, fastlands, slowlands, battle lands, Castles, snarls, Starting Town and the rest) are judged on your battlefield, hand and turn as they enter. Shock lands always come in untapped: Goldfish pays the life. Conditions it can’t check, like an opponent’s life total, count as tapped.

Lands make the mana their text says: Maze of Ith makes none, Ancient Tomb and the bounce lands make two, and Tron, Gaea’s Cradle, Nykthos, Cabal Coffers and Temple of the False God make what your board lets them (Goldfish pays Nykthos’ and Coffers’ activation from your other mana when it nets more). A bounce land taps the land it returns for mana first, and that mana floats for the turn; it returns your least needed land. A Karoo returns an untapped land of its type, or is sacrificed when you have none. Lotus Field sacrifices your two least needed lands, tapping them for mana first. Exotic Orchard makes any color, since a Commander table always has opponents with lands; Fellwar Stone, a rock with the same text, follows the same rule.

Fetch lands: a fetch that costs no mana (Misty Rainforest, Evolving Wilds, Fabled Passage) cracks as soon as it can tap, every time, and finds only what its text allows: Evolving Wilds finds basics only. The land it finds enters tapped if the fetch says so, or by its own rule otherwise. A fetch that costs mana (the Panoramas, Myriad Landscape, Krosan Verge) taps for {C} and cracks at the end of the turn when you have mana left over to pay for it. The turn’s events read “Cracked Misty Rainforest for Forest”, or “Evolving Wilds found nothing” when the library has nothing it may find.

Mana available counts your untapped lands, rocks, dorks and Treasures, plus any mana left floating this turn (the second mana from a Sol Ring that paid for a one-mana rock, for example). A dork can’t tap for mana on the turn it’s cast. One-use rocks (Lotus Petal, Mana Vault) and mana that pays only for creatures (Somberwald Sage) aren’t counted. A ritual’s leftover mana counts only while a commander is still waiting to be cast, since that’s all it can pay for. Reloading the page shows the same Mana available and the same tapped cards as the turn did.

Badges: the card you drew for the turn is marked Drawn, and keeps that badge if it was played the same turn (with another copy still in hand, the one in play shows Played); cards ramp drew aren’t marked. Every other land that entered this turn (a fetch land’s find included) and every card the turn cast is marked Played, and lands a ramp spell found (Cultivate, Rampant Growth) are marked Found. Screen readers hear the badge at the end of the card’s name.

The turn counter shows the current turn, and the session’s Lands drawn and Spells drawn stats count every card you drew, including the ones ramp drew (Big Score, Explore).

When your library runs out, the turn shows Your deck ran out, with no Next turn; reloading the page shows the same.

Commander Availability

The simulator casts your commander on the first turn it can pay for it, ahead of any ramp that would use the mana it needs. If casting a rock first would make the mana (Sol Ring with four lands for a five-mana commander), it casts the rock and then the commander that same turn. After that, later turns cast ramp only.

• Commander - The turn Goldfish cast your commander

Once cast, your commander sits on the battlefield in its own Commander group, and it counts like any other permanent there: Mox Amber taps for its colors, Gaea’s Cradle and Elvish Archdruid count it, and Nykthos counts its pips. A commander whose text makes mana like a mana creature’s (a Selvala, an Elf that taps for {G}{G}) makes it from the turn after it’s cast. Commanders that make Treasures don’t make them in Goldfish.

Partners: with two commanders (partners, Friends forever, or a Background), each is cast on its own, and the stat reads both turns, slot 1’s first (“T4 · T3”, or “T5 · —” while one isn’t out). Automated runs keep playing until both are cast.

Odd mana costs: a {2/W} pip takes a white mana if you have one left, otherwise two of any mana. A Phyrexian pip ({B/P}) takes its color if any is left after the rest of the cost, otherwise 2 life; the turn’s note says how much (“Cast K’rrik · 2 life”). Goldfish doesn’t keep a life total. A snow pip ({S}) needs mana from a snow permanent.

This helps evaluate: - Whether you have enough mana rocks/ramp - If your mana base supports commander cost

Example: - 4-mana commander - Turn 4: Goldfish casts the commander (4 lands)

Mana Rocks

Each rock makes what its card says. Sol Ring makes two colorless, Thran Dynamo three, and a Signet costs {1} to tap, so it nets one mana (one of each of its two colors). Gilded Lotus makes three of a single color. Coldsteel Heart and other “choose a color” rocks pick the commander color your board makes least, and the tile and turn notes name it.

• One use: Lotus Petal, Lion’s Eye Diamond, Jeweled Lotus and the monoliths (which never untap) are tagged One use. They wait on the battlefield and are spent only to cast your commander. Lion’s Eye Diamond is spent last, and only when nothing else pays, because it discards your hand.
• Moxen: Mox Diamond is cast only when you have a land to discard after your land drop. Chrome Mox imprints a colored card you can’t cast this turn and makes its colors. Mox Opal needs three artifacts, and Mox Amber needs a legendary creature or planeswalker.
• Counters: Everflowing Chalice is kicked as many times as your spare mana allows and makes one colorless per charge counter. Pyramid of the Pantheon gets a brick each turn you can pay {2}, then makes three mana. The counter shows on the card.
• Suspended: Sol Talisman, Lotus Bloom and Mox Tantalite are suspended when you have spare mana, and wait in their own Suspended zone with their time counters. Each turn one comes off; when the last does, the rock arrives and can tap that turn.
• A rock Goldfish can’t read stays in your hand, so it never makes up mana.

Mana Dorks

Mana dorks (creatures that make mana) are the cards Icarian’s own card tags mark as mana creatures, and each makes what its text says:

• Auto-play: As many dorks and rocks per turn as your mana pays for, after the land, around the commander
• Summoning Sickness: Creatures have summoning sickness and can’t tap the turn they’re played
• Mana: Llanowar Elves makes {G}, Birds of Paradise one of any color. Elvish Archdruid and Wirewood Channeler count your Elves, Sanctum Weaver your enchantments, and Kami of Whispered Hopes and Marwyn make as much as their printed power, all of one color. Somberwald Sage’s mana pays only for creatures; a dork whose mana pays only for abilities or one tribe’s spells makes none in Goldfish. Lotus Cobra adds its mana as each land enters, and Gilded Goose taps with a Food. A dork Goldfish can’t read makes one mana of its colors.
• Battlefield Display: Dorks appear in their own group on the battlefield, after lands and mana rocks
• Statistics: Mana from dorks, best turn (see Session Statistics)

Example Turn Sequence: - Turn 1: Play Forest → 1 mana available - Turn 2: Play Plains, cast Llanowar Elves (1 CMC) with the Forest → 1 mana available (the elf has summoning sickness) - Turn 3: Play Mountain → 4 mana (3 lands + the elf, its summoning sickness gone) - Cast Arcane Signet (2 CMC) with a land and the elf → 3 mana available (2 lands + the Signet)

Auto-Play Priority: 1. Play one land (if available) 2. Cast the commander, along with any ramp that pays for it this turn 3. Cast as many dorks and rocks as your mana allows, ordered for the most mana next turn

The simulator accurately accounts for summoning sickness, ensuring dorks can’t tap until the turn after they’re played (unless they have haste).

Land Ramp

Goldfish also casts land ramp and does what each card says:

• Land searches (Cultivate, Rampant Growth, Nature’s Lore, Farseek, Wood Elves, Sakura-Tribe Elder, Burnished Hart): it finds the lands the card names, tapped or untapped as written, onto the battlefield or into your hand (Cultivate’s second land shows in hand marked Found). “Basic land” means a basic; “a Forest card” can be a Breeding Pool. It picks lands for the colors your commander and hand still need. A search with nothing to find isn’t cast. Sakura-Tribe Elder is sacrificed the turn it comes down; Burnished Hart and Wayfarer’s Bauble at the end of a turn with mana left to pay for them.
• Searches with a twist: Sowing Mycospawn searches as it’s cast, and Tempt with Discovery finds one land (your opponents decline the offer).
• Extra land drops (Exploration, Azusa, Explore) are used after the turn’s casts, one land at a time. Growth Spiral, Walking Atlas, Arboreal Grazer and Spelunking put a land from your hand onto the battlefield without using a drop; Arboreal Grazer’s enters tapped, so it puts a land that would enter tapped anyway. Spelunking draws a card first, but Goldfish doesn’t apply its “Lands you control enter untapped.” With Oracle of Mul Daya or Courser of Kruphix out, the top card of your library is a candidate for each land drop.
• Land auras (Wild Growth, Utopia Sprawl, Overgrowth, Fertile Ground) go on an untapped land they can enchant, never a fetch land. The land then makes its mana plus the aura’s, and its tag says what the aura adds (“Land +G”). Utopia Sprawl picks the commander color your board makes least. A bounce land or Karoo returns an enchanted land only when no other land will do; when an aura goes with its land, the turn says so (“Utopia Sprawl went to the graveyard”).
• Ramp cast this way that makes no mana itself (Wood Elves, Exploration, Oracle of Mul Daya) sits in the Other zone.
• Ramp Goldfish can’t read, or with an extra cost like Harrow’s sacrifice, stays in your hand.

Treasure and Rituals

Goldfish plays as if there are three opponents who do nothing: each draws a card on their turn, never pays for anything you offer, and controls nothing.

• Treasure makers make Treasures when their card says so: as they enter or resolve (Big Score, Brass’s Bounty), when an opponent draws (Smothering Tithe makes 3 at the start of each of your turns), at your upkeep or end step, when a land enters (Tireless Provisioner), or when you cast a spell (Storm-Kiln Artist). Black Market Connections makes one at the start of each of your turns, Lotho on the second spell you cast in a turn, and Ganax when it enters. Xorn makes one more Treasure each time Treasures are made; Academy Manufactor adds none, since Goldfish never makes the Clue or Food it would turn into one. Treasure makers that make no mana themselves sit in the Other zone.
• Treasures show as one tile in Mana rocks (“Token ×3”). A Treasure can pay for any card the turn’s plan casts, the commander included, but Goldfish spends them only after every land, rock and mana creature, and a chip says when one is sacrificed. Cards cast after the plan with mana left over, and activated abilities (Burnished Hart, paid fetch lands, Pyramid of the Pantheon), never use a Treasure. Mana available counts them; Mana from rocks doesn’t.
• Big Score and other “discard a card” spells discard your highest mana value nonland card. With no other nonland card in hand, they aren’t cast.
• Rituals (Dark Ritual, Seething Song) are cast only on a turn their mana lets the commander come down, and their mana pays only for the commander.
• Never cast: a card whose Treasures come only from combat, a creature dying or an activated ability, since Goldfish has no combat and nothing dies; makers that count what opponents control (Dockside Extortionist makes none); rituals whose amount depends on a count (Inner Fire) or that limit what their mana pays for (Geosurge). These stay in your hand.

Session Statistics

Each session shows these stats:

Hand Quality

• Hands drawn - Hands drawn this session, mulligans included
• Mulligans - Mulligans taken
• Opening hand avg MV - Average mana value of the opening hand
• Lands in opening hand - Lands in the opening hand

Draws

• Lands drawn - Lands drawn after the opening hand, including draws from ramp
• Spells drawn - Nonland cards drawn after the opening hand, including draws from ramp

Mana Stats

• Mana from rocks, best turn - The most mana your mana rocks could make in any one turn of the session, after their activation costs; rocks used once (Lotus Petal, Mana Vault) and Treasures aren’t counted
• Mana from dorks, best turn - The most mana your mana creatures made in any one turn: the ones that could tap, plus what landfall creatures added as lands entered

Both mean the same for a session you play and for an automated run.

Commander Stats

• Commander - The turn your commander was cast (one per commander for partners)

Interpreting Results

Too Many Mulligans

If you mulligan more than 20-30% of hands: - Problem: Poor mana base or inconsistent curve - Solution: Add more lands, better ramp, or fix mana curve

Can’t Cast Commander

If you can’t cast commander until turn 6+: - Problem: Not enough mana acceleration - Solution: Add mana rocks, ramp spells, or land ramp

Too Many Lands

If you draw lands 50%+ of the time after turn 5: - Problem: Too many lands in deck - Solution: Cut 2-3 lands, add card draw or filtering

High Average CMC

If opening hand average is 4+ mana: - Problem: Curve is too high, hands are clunky - Solution: Add more low-CMC cards (1-2 mana)

Low Average CMC

If opening hand average is below 2 mana: - Problem: Too many cheap cards, not enough powerful plays - Solution: Add higher-impact cards, remove filler

Goldfish Session History

View past goldfish sessions:

1. Open Goldfish and click History
2. See all previous sessions with statistics, newest first
3. Click Run 10 automated to let Icarian play ten hands for you; they’re marked Auto with why each one stopped: Commander ready (Commanders ready for partners), Deck ran out, Stopped at turn 20, or Failed when a run hit an error. Until a run finishes it shows Waiting or Running. Each run mulligans once when its hand has 0–1 or 6–7 lands, taking the free first mulligan (it keeps all 7), then plays until your commander (or both partners) is cast, the deck runs out or turn 20 ends

This helps track: - How deck changes affect consistency - Whether fixes improved performance - Long-term average statistics

Limitations of Goldfishing

Goldfish testing doesn’t simulate:

• Opponent interaction (removal, counterspells): opponents do nothing but draw a card each turn. They never play lands, so Burgeoning never triggers
• Multiplayer politics
• Combat scenarios
• Board state complexity

Use goldfish testing for: - ✓ Mana curve evaluation - ✓ Consistency testing - ✓ Opening hand quality - ✓ Commander availability

Use playtesting (real games) for: - ✓ Interaction with opponents - ✓ Board state management - ✓ Political decisions - ✓ Sideboard decisions

Best Practices

1. Run multiple sessions - Test at least 10 opening hands
2. Track changes - Goldfish before and after deck edits
3. Simulate realistic keeps - Mulligan hands you’d actually mulligan in a game
4. Note patterns - Look for recurring problems (always flooding, always missing lands)
5. Compare to ideal - Your deck should cast commander by turn 4-5 and have plays every turn

Example: Identifying Issues

Session Results

• 10 opening hands tested
• 4 mulligans in those 10 hands ⚠️
• About 2 lands in each opening hand ✓
• Commander cast around turn 6 ⚠️
• Opening hands average 4.2 mana value ⚠️

Diagnosis

• High mulligan rate → Inconsistent hands
• Commander late → Not enough ramp
• High CMC → Curve too high

Fixes

1. Add 3 mana rocks (Sol Ring, Arcane Signet, Fellwar Stone)
2. Cut 3 high-CMC cards (6+ mana)
3. Add 2 more lands

After fixes, re-goldfish to verify improvement!