蓮麻坑河是河岸長有植物的典型低地溪流，溪流水流緩慢而河道淺，主要是天然的溪流主要流經廢棄的農業用地。而由於受到不同的人類活動及渠務工程影響，相類似的本地天然溪流已經變得越來越少。蓮麻坑河紀錄有20種淡水魚類（一生都在淡水中度過的魚類），是全港錄得最多初級性淡水魚種類的地方。而在這20個品種當中，有15種是原生物種，若占有這裡魚類數目的一半。而其中一些更具有相當髙的保護價值，例如蓮麻坑河有豐富數量的斯氏波魚，而斯氏波魚是一種曾經被認為已於本地絕種的稀有魚類；另外還記錄有在低地溪流中的罕見的線細鯿和大刺鰍，及野非常外稀有的月鱧。

It is a typical lowland freshwater stream characterized by slow flowing and shallow channel bordered with riparian vegetations. The stream course is largely natural and its drainage basin is mainly abandoned agricultural land. Similar stream habitats in Hong Kong with such characteristics are becoming rare due to water pollution by human activities and channelization works.
The Lin Ma Hang Stream supports 20 primary freshwater fish species (i.e. fishes that spend their entire life in freshwater) and was reported as the most species-rich site in Hong Kong in terms of primary freshwater fishes. Among these 20 fish species, 15 of them are native to Hong Kong, representing 50% of all such species, and some are of conservation value. For example, Rasbora sterineri 斯氏波魚 is locally rare and was once thought to have been extinct locally but the species now has a thriving population in the Lin Ma Hang Stream. Rasborinus lineatus 線細鯿 and Mastacembelus armatus 大刺鰍 have very limited record in lowland streams, and Channa asiatica 月鱧 is lovally uncommon in the wild.