Filipino Sour Fish Soup (Sinigang na Isda)

Filipino sour fish soup, often called sinigang na isda, is a bright, savory broth simmered with fish, vegetables, and a tarting agent such as tamarind. This practical version uses tamarind soup mix for dependable sourness, with green beans, radish, tomato, and leafy greens; families and regions vary the fish and vegetables.

Ingredients

1½ lb (680 g) firm white fish, such as salmon, snapper, or cod, cut into 4 portions
8 cups (1.9 L) water
1 medium yellow onion (about 150 g), peeled and cut into wedges
2 medium tomatoes (about 300 g), cut into wedges
1 small daikon radish (about 250 g), peeled and sliced into ¼-inch (6 mm) rounds
1½ tablespoons (22 ml) fish sauce, plus more to taste
1 packet (about 40 g) sinigang tamarind soup mix, or the amount specified on its package for 8 cups (1.9 L) water
8 oz (225 g) green beans, trimmed and cut into 2-inch (5 cm) lengths
1 small eggplant (about 200 g), cut into ½-inch (1 cm) rounds
1 bunch (about 100 g) water spinach (kangkong), tough stems removed and leaves cut into manageable lengths
2 green onions, thinly sliced, for serving
Steamed rice, for serving

Instructions

Prepare the vegetables and fish. Pat the fish dry and check for pin bones; leave the skin on if you like, as it helps the portions hold together. Keep the pieces chilled until they go into the pot.
In a large pot, combine the water, onion, tomatoes, daikon, and fish sauce. Bring to a boil over medium-high heat, then lower the heat to maintain a steady simmer. Cook for 10 minutes, until the daikon is beginning to turn tender.
Stir in the tamarind soup mix, following the packet’s dilution guidance if it differs from the amount listed. Simmer for 2 minutes, then taste the broth. Add a little more mix for sharper sourness or a splash of water if it is too intense. Soup mixes vary in salt, so wait before adding extra fish sauce.
Add the green beans and eggplant. Simmer gently for 5 minutes, until they are nearly tender. Avoid a hard boil, which can break up the vegetables and make the broth cloudy.
Lower the fish portions into the broth in a single layer. Simmer gently for 6–8 minutes, depending on their thickness, turning them only if needed. Check the thickest part of each portion with a food thermometer; fish should reach the USDA FSIS safe minimum internal temperature of 145°F (63°C). The flesh should also look opaque and separate easily with a fork.
Stir in the water spinach and cook for 1–2 minutes, just until wilted. Taste the broth and adjust with fish sauce or a little water. Serve hot, topped with green onion and accompanied by steamed rice.

Tips

Choose fish that holds together. Salmon, snapper, cod, and other firm fillets work well. Very thin fillets or delicate fish can flake apart; add them near the end and handle them as little as possible.
Adjust sourness gradually. Tamarind mixes differ by brand and can be salty. Start with the package amount for your volume of water, taste, then add more in small increments rather than seasoning the broth all at once.
Use the right substitute. Fresh tamarind pulp is traditional in many versions: simmer about 3 oz (85 g) pulp in water until soft, mash, and strain the liquid into the soup, adjusting to taste. If using calamansi or lime instead, add juice gradually at the end; it gives a brighter citrus tang rather than tamarind’s rounded sourness.
Keep the simmer gentle. Once fish is in the pot, bubbling should be quiet. A rolling boil can break the portions apart and make timing harder to control.

Serving Suggestions

Serve the soup as soon as the greens wilt, with a bowl of hot steamed jasmine or other plain rice to soak up the sour broth. Put extra fish sauce, sliced chilies, or calamansi wedges on the table so each person can season their own bowl. If serving a group, ladle vegetables and broth first, then transfer the fish carefully to keep its portions intact.

Variations

Use taro, okra, bok choy, or mustard greens in place of some vegetables, adding each according to how long it needs to soften. Kangkong can be difficult to find outside Filipino or Southeast Asian groceries; baby spinach is a convenient substitute, though it wilts faster and has a softer texture. For a more traditional sour base, strained tamarind pulp can replace the soup mix. Some cooks use green mango or calamansi for a different tart profile, while others add long green chilies for aroma and mild heat. These are regional and household variations, not requirements.

Storage and Reheating

Refrigerate leftovers within 2 hours of cooking in a covered, shallow container. The soup keeps for 3–4 days in the refrigerator. Fish can become drier and more fragile after reheating, so store portions in their broth and warm only what you plan to eat. Reheat gently in a saucepan until the leftovers reach 165°F (74°C), checking with a food thermometer; avoid repeated heating and cooling. The soup can be frozen for up to 2 months for best quality, though the vegetables may soften and the fish may flake more after thawing. Thaw in the refrigerator, then reheat to 165°F (74°C).

Frequently Asked Questions

What fish is best for sinigang na isda?
Choose firm fish that can simmer without falling apart. Salmon, snapper, cod, and similar fillets are practical options. Bone-in fish can add flavor, but take care when serving and eating around the bones.

Can I make the soup without a tamarind packet?
Yes. Use strained tamarind pulp, or add another souring ingredient such as calamansi or lime a little at a time. The flavor will differ, and you may need to adjust the amount of fish sauce to balance it.

Can I use frozen fish?
Yes. Thaw it safely in the refrigerator, then pat it dry before adding it to the simmering broth. Do not add a large block of frozen fish directly to the pot, since it can cool the broth and cook unevenly.

How do I keep the fish from breaking apart?
Use thick portions, lower them into gently simmering broth, and avoid stirring after they go in. Cook just until the thickest part reaches 145°F (63°C), the USDA FSIS safe minimum for fish.

Is sinigang supposed to be very sour?
It should taste distinctly tart, but the exact balance is a matter of preference. Tamarind products vary, so season in stages and taste before serving; fish sauce adds saltiness and savoriness, not sourness.

Can I make it ahead?
You can prepare and cut the vegetables ahead, and make the broth before adding the fish. Refrigerate prepared ingredients promptly. For the best fish texture, add and cook the fish shortly before serving, then wilt the greens at the end.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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