Amanzi wekhwalithi anomthelela ekukhuleni kweemfesi (amanzi wekhwalithi ehle = ukukhula msinya), ukuba namagulo nokunambitheka kunye nombala weemfesi. Ikhwalithi yamanzi ihlolwa ngokuqala amafekthara amane alandelako:
Amazinga womtjhiso wamanzi
Amazinga womoya wokuphefumula asemanzini
Amazinga we-amoniya (ammonia) esemanzini
I-pH yamanzi (amazinga we-esidi (acidity) nofana we-(alkalinity))
Imiraro eminengi yamanzi wekhwalithu ebakhona lokha nakusetjenziswa ihlelo lokufuya iimfesi ngokusebenzisa amanzi afretjhi elibizwa nge-freshwater fish farming ibangelwa kuphunguleka komoya, amazinga aphezulu we-amoniya (ammonia) nofana we-pH emanzini. Imiraro lee ihlotjaniswa namazinga we-microscopic algae emanzini.
Ukukhula kwama-algae kuthembele enanini lezakhamzimba ezinikela amandla ama-Nutrients- nitrogen (N) ne-phospherus (P) ezisemanzini. Izakhamzimba lezi zingena ngemanzini ngo:
Ngomthombo wamanzi (Amanzi agelezela ngedamini).
Iinzibi eziza ngomlambo lokha nakunenkhukhula.
Ukudla okudliwa ziimfesi lokha ngesikhathi sokukhiqiza.
Amazinga Womtjhiso Afuneka lokha Nakufuywa iimfesi
Umhlobo wefesi we-Trout ukhula khulu lokha amazinga womtjhiso nakahlangana na 14 no 18°C 16°C kodwana iinlwane ezinegazi elitjhisako njenge-sharptoot catfish zikhula kuhle emanzini atjhisakhudlwana nge-(20 - 30°C) begodu zomhlobo we-tilapia zibhederisa amanzi anamazinga womtjhiso aphezulu alingana na 24 - 34°C.Umhlobo weemfesi ze-Trout ziyawasaba amanzi atjhisako. Amazinga womtjhiso angaphezulu kwe 20°C angabangela bona iimfesi zomhlobo we-Trout zilise ukukhula begodu zidale nemiraro eminye ekhambelana nokukhiqiza, efana namazinga aphezulu wamalwelwe nemiraro yomoya wokuphefumula, kuhlathulula uHenk Stander onguhlokokulu wamathekniki we-Aquaculture: Department of Animal Sciences, Stellenbosch University.
Imiraro lee (amazinga aphezulu wamalwelwe nokwehla komoya wokuphefumula) unobangela wayo kuma-microscopic algae amanengi asemanzini afuthumeleko. Lokha amazinga nakafika ku 21°C ukuya phezulu, kufanele atjhetjwe ukuvikela bona iimfesi zingafi nokunindwa bulwembu. Algal taints abangelwa ma-blue-green algae amanengi ngenani abangelwa mazinga aphezulu womtjhiso nezakha mzimba ezinikela amandla ekhona. Ubulwembubu bukhipha amakhemikhali anesiqa esinuka njengomhlaba (earthy-smelling substance), geosmin. Isiqesi simunya ziimfesi begodu sitjhugulula indlea ifesi enambitheka ngayo.
Amazinga Womoya Wokuphefumula lokha Nakufuywa iimfesi
Imiraro yomoya yokuphefumula ibangelwa ma-microscipic algae. Ama-algae amancani aya-photosynthesize bekakhiqize umoya wokuphefumula. Nakunamazinga we-alagae ajayelekileko, angeze kwaba nemiraro.
Nangabe amazinga we-algae nakangaya phezulu, amazinga womoya wokuphefumula ebusuku angehla bekabe ngaphasi kuka 5 mg/L begodu kubenemiraro yomoya wokuphefumula emanzini ngelanga elilandelako ekuseni.
Kwesibili, nakwenzeka inani le-alage elincani lifa ngokuphazima kwelihlo (ngonobangela wobujamo bezulu obunamafu nofana kufufuzelwe nge-algaecides), amaqhiwani we-aerobic azokukhula khulu arhelebhe ekuboliseni i-alagae efileko. Amaqhiwani we-aerobic adla umoya wokuphefumula ehlise amazinga womoya khulu asemanzini begodu abangele ukugandeleleka ngokomkhumbulo eemfesini.
Amazinga we-Amoniya (Ammonia) Emanzini Afretjhe
I-amoniya (ammonia) yenzeka emhlobeni onetjhefu nonganatjhefu i-(ionised ammonia) kodwana umhlobo onganatjhefu esikhathini esinengi ungaphasi kwe 10% ye-amoniya (ammonia) epheleleko. Emanzini afuthumeleko alingana na (+20°C) ane-pH ya (8.5), amazinga we-amoniya (ammonia) azokukhuphuka.
Amazinga we-amoniya (ammonia) esikhathini esinengi akenzi imiraro emadamini, ngaphandle kwemadamini angatjhingeli khulu we (5 m nofana ngaphasi) nalaya afaka amanzi wezulu nofana abuya kwamanye amadamu enza ngaphasi kwephesente linye ngonyaka. (“Annual turnover” izinga amanzi wedamu angezeleleka ngalo ngamanzi abuya ezulwini nakamanye amadamu qobe nyaka)
I-pH Yamanzi Wedamu
Ifekthara ebalulekileko engakhulisa amazinga we-pH wobulwembu. Ubulwembu obunengi bukhulisa amazinga we-pH khulukhulu emadamini wemaplasini amancani kufikela emazingeni angaphezulu kwe-pH 9 (khukhukhulu ngemva kwamadina). Lokhu kubangelwa kususwa komoya ongakahlwengeki obizwa nge-carbon dioxide ngendlela yekambiso ye-photosynthesis. I-pH ephezulu ngalendlela ingafaka iimfesi ngaphasi kwegandeleleko lomkhumbulo.
Ukulungisa amazinga laa, ukutjhugululwa kwamanzi kuyafuneka, faka amanzi afretjhe nakukghonekako. Nangasinjalo, faka i-barley straw.
Translated by Busisiwe Skhosana