Calitatea apei din iaz, pe timp de vara

Summer water quality for pond fish

Putem spune cu certitudine ca vara este cel mai bun moment pentru a amenaja si ingriji un iaz. Este vremea in care pestii sunt foarte activi, iar tu poti profita ca, in serile lungi si calduroase, sa admiri activitatea frenetica din iaz. Dupa stresul prin care treci pentru a igriji iazul in delicata perioada de primavara, vara este momentul in care te poti relaxa si sa-ti oferi un pic de timp pentru a-ti admira munca. Cu toate acestea, exista cateva probleme care pot aparea si in anotimpul cald, mai ales din cauza cresterii excesive a algelor din iaz.

Una dintre proprietatile apei este aceea ca, cu cat se raceste mai mult, cu atat poate retine mai mult oxigen dizolvat. O mostra de apa la temperatura de 5 grade C este saturata cu oxigen in cantitate de 12.76 mg/l. Pe de alta parte, o mostra de apa la o temperatura de 25 grade C este saturata in momentul in care contine doar 8,24 mg/L de oxigen.

Ce implicatii au aceste lucruri pentru iaz? 

In primul rand, cand apa este mai calda, prezenta oxigenului este si ea mai redusa, motiv pentru care pestii devin mult mai activi si necesita mai mult oxigen. Pentru fiecare 10⁰C in plus, rata metabolica a pestilor se dubleaza.

Si nu doar pestii sunt cei care au nevoie de oxigen, ci si activitatea filtrului antibacterian va fi influentata si dictata de temperatura – cu cat apa este mai calda, cu atat mai repede metabolizeaza.

Couple this with a greater production of ammonia by the fish, and the increased overall consumption of oxygen by living organisms in the pond, the amount of oxygen available is at an annual low.

Pentru a manageria aceasta problema a oxigenului este esential sa te asiguri ca, pe tot parcursul lunilor de vara, apa din iaz este oxigenata. Pentru acest lucru ai nevoie de kitul Tetra Test Oxygen pentru a analiza nivelul de oxigen si a te asigura ca ramane la o valoare care satisface necesarul cerut de pesti, dar si de filtrul de oxigen.

Concentratia de oxigen poate fi exprimata in mg/L, but this fails to account for the saturation value of oxygen in the water. A more convenient expression is percentage saturation. For example, freshwater at 25°C holds 8.24 mg/L of oxygen at 100% saturation, if the level dropped to 6 mg/L then the sample would be 72.8 % saturation.

As such, during the summer months, the pond keeper must be especially vigilant of dissolved oxygen levels in the pond. Regular testing is useful, thorough aeration of the water by airstones, venturi’s, waterfalls and/or fountains is essential. During especially hot and humid days, the dissolved oxygen level can be at its lowest, and extra vigilance is required. Always make sure you have hit a minimum of 60% saturation but strive for a value nearer to 80%. The closer biofiltration chambers are to saturation with dissolved oxygen the better they function.

Another problem that can arise in ponds in the summer is blooms in the growth of unsightly blanket weed and green water algae. These primitive plants have basic requirements including dissolved nutrients such as nitrate and phosphate and sunlight to allow them to photosynthesise. In many ponds, algae become a real problem in the summer as the sunlight reaches the correct intensity and shines for a sufficiently long period of time to allow algal growth to proceed at a maximal rate. Tetra Pond AlgoFin and AlgoRem can help to safely and effectively treat algae problems.

Apart from looking unsightly, algae can cause numerous water quality based problems. On a basic level, algal cells and strands of blanket weed soon clog filtration systems, leading to the pond keeper having to perform laborious routine maintenance to keep the life-support-system of the pond running efficiently.

Down at a chemical level, the pond water is being profoundly influenced by the growth of algae. The photosynthetic processes which occur only in daylight hours see the liberation of oxygen and the uptake of carbon dioxide. These processes occur at the same time as the normal respiration of the plant, but there is an overall increase in oxygen and decrease in carbon dioxide in a pond with heavy growths of plant life.

At night photosynthesis stops, but respiration continues leading to a decrease in oxygen levels and increases in carbon dioxide, a trend that continues until sunrise.

Ce inseamna toate astea pentru pesti?

Firstly, the oxygen level in the pond will be far from stable, lakes heavily choked with algal growth have been recorded fluctuating from a supersaturated 169% down to a low of 39% sat. This instability would cause chronic stress to fishes and would need to be remedied.

Another problem is the carbon dioxide release which increases at night. The chemistry of carbon dioxide in water is very complex, but can generally be considered to lower the pH as it leads to the formation of carbonic acid, meaning that more carbon dioxide leads to a lower pH.

The pH is held stable by the buffering system or carbonate hardness (KH) in the water. Ponds with a good strong KH (>6 °H) can resist the change in pH for a decent length of time, as the KH can buffer the carbonic acid. Remember though that KH can become exhausted and is best replaced by a water change with hard to moderately hard water. If you live in a soft water area of the country then KH can be raised by placing a cockle or oyster shell into the final stage of the filtration system. Alternatively, you can improve water quality by adding Tetra Pond WaterBalance which helps to maintain the correct water conditions, stabilising pH and KH to promote a healthier pond environment.

Therefore, a pond choked with algae is a potentially dangerous environment for the pond as well as an eyesore in the garden of the pond keeper. The action plan involves getting rid of the algae, ensuring the oxygen level is not fluctuating by vigorously aerating the water, especially at night. And finally ensuring the pond is not suffering daily fluctuations in pH by maintaining a good level of KH in the pond water.

What about aquaria?

This unfortunate property of water to hold less oxygen in warmer water also impacts aquaria but for the majority of tanks this should not be an issue if necessary precautions are taken. A tropical tank will be heated to around 25⁰C though in a small urban flat in high summer the room temperature may rise well above this. Measures taken to keep the room at a comfortable temperature for the human occupants will also benefit the fish. Close curtains and blinds to block direct sunlight and leave windows open if you’re able to. Aerate the tank as much as possible at this time of year, monitor the tank temperature and fish behaviour closely. Look out for signs of respiratory distress such as lethargy and gasping at the water surface.

Goldfish in unheated tanks should be able to tolerate water temperatures rising above 25⁰C, but again there will be a need to aerate the tank often. Temperate tanks containing fishes such as White Cloud Mountain minnows will be less forgiving.

Marine aquarium keepers will need to be especially vigilant as overheating of their aquaria can be a common problem especially due to the strong lighting used and fish/invertebrate distress can arise – these tropical marine animals simply cannot tolerate temperatures encountered in some indoor environments in the summer. If room temperatures cannot be kept below 25⁰C in high summer, then an automatic aquarium chiller must be installed or the fishkeeper must be ready with ice packs, a fan or cooled artificial seawater to manage the temperature manually.