Matsya Purana 58.56

58.56

evameṣu purāṇeṣu taḍāga vidhirucyate.. 58.50 ..

Afterwards, the worshipper should feast either 1,000, 800, 50 or 20 Brâhmaṇas, according to his means, which is the way of consecrating the tank, as described in the Purâṇas.—50.