Learn Spanish (Latin America): Si compro el triple de pescado, lo congelo.

When you use a noun like triple to describe a quantity of another noun, you must connect them with de. You can think of it as saying "the triple of fish". If you leave out de, the phrase is grammatically incomplete in Spanish.

Why is there an el before triple?

Words like doble, triple, mitad, and tercio act as nouns when expressing these kinds of proportions, so they require a definite article. Because triple is a masculine noun, it takes el.

Since si means "if", why don't we use the subjunctive for compro?

When an "if" clause talks about a highly possible or routine event in the present or future, Spanish uses the normal present tense (the indicative). You only use the subjunctive after si for unlikely or impossible hypothetical situations, like "If I had a million dollars".

What does lo refer to in lo congelo?