水差 (Chúi-chhi)是 (sī)蠓仔 (báng-á)的 (ê)幼蟲 (iù-thâng),通常 (thong-siông)生活 (seng-oa̍h)佇 (tī)未 (bē)流動 (liû-tōng)的水域 (chúi-e̍k)。只要 (Chí-iàu)有 (ū)積水 (chek-chúi)的所在 (só͘-chāi),攏 (lóng)有可能 (khó-lêng)予 (hō͘)蠓仔放卵 (pàng-nn̄g),造成 (chō-sêng)水差的生湠 (seⁿ-thòaⁿ)。
熱天時 (Joa̍h-thiⁿ-sî)若 (nā)落 (lo̍h)過 (koè)大雨 (tōa-hō͘),就 (to̍h)會 (ē)有可能佇積水的區域 (khu-e̍k)爆發 (po̍k-hoat)天狗熱 (thian-káu-jia̍t)抑是 (ah-sī)其他 (kî-thaⁿ)由 (iû)蠓蟲 (báng-thâng)所 (só͘)傳染 (thoân-jiám)的病症 (pēⁿ-chèng)。一般 (It-poaⁿ)來講 (lâi-kóng),只要清除 (chheng-tû)積水,雨 (hō͘)水差無法度 (bô-hoat-tō͘)生存 (seng-chûn),就 (tio̍h)會當 (ē-tàng)減少 (kiám-chió)遮的 (chia-ê)傳染病 (thoân-jiám-pēⁿ)的發生 (hoat-seng)。
孔雀魚 (Khóng-chhiok-hî),三斑 (sam-pan),大肚仔 (tōa-tō͘-á)等等 (téng-téng)的魚仔 (hî-á),攏會食 (chia̍h)水差,對 (tùi)水差數量 (sò͘-liōng)的減少有真大 (chin-tōa)的效果 (hāu-kó)。