Koi lovers don't make mistakes, of course. But should circumstances be so unfortunate as to cause an inexperienced newbie to make a mistake, this article might help them!
1. Save water by diverting water from the roof into your pond!
The idea sounds good, but it isn’t really! What does your car look like when it has stood outside for a few days without rain in spring and summer? It is completely covered with pollen and pollen dust. And that's exactly what happens on your roof. This nutrient broth is then washed into your pond the next time it rains. If you are an algae lover, this is the way to go! In addition, rainwater, painstakingly turned into acid rain by humans due to increased CO2 levels in the air, flows through your often copper-rich gutters. Due to their low pH value, copper ions are dissolved out of the gutter and enter your pond. From 0.3 mg/l copper, this is not only deadly for all microorganisms, but also for the fish! On the other hand, you’ll have less algae thanks to the copper.
2. Use well water, it's cheaper than tap water!
This is true, of course, but please check your well water before adding it into your pond. Many wells are not approved for drinking water production, for example, for legitimate reasons. Be sure to check how much iron (Fe test, target value 0.2 mg/l) your well water contains. The two algae nutrients nitrate (NO3 test, target value 5 mg/l) and phosphate (PO4 test, target value 0.1 mg/l) are also often found in well water, especially if there are intensively fertilised agricultural areas in the region.
3. You don’t need water changes – the rain will refill the pond!
Yes, we humans are basically lazy and water changes are not one of our favourite activities. Besides, tap water costs money! On the other hand, rainwater is practically distilled water, so it contains no minerals. However, some minerals are essential for the survival of our pond. First and foremost is the carbonate hardness. The carbonate hardness stabilises the pH value in the pond. With a KH below 5 °dKH, the pH value of your pond water will happily fluctuate between, for example, 6.0 in the morning and 10 in the evening. Since the pH value is a logarithmic value, this means an increase or decrease in acidity by a factor of 10,000!!! The carbonate hardness is therefore the life insurance for your pond and should definitely be checked regularly. However, it is strongly diluted in the pond by heavy rainfall and also consumed by algae growth due to CO2 deficiency (biogenic decalcification). There are good products available in specialist shops, such as JBL StabiloPond, with which the KH can be brought to the correct level. Therefore, please do not only rely on rainwater to fill up the evaporated water, but also carry out a partial water change with tap water from time to time!
4. High levels of ammonia are the greatest danger for the koi!
The issue of ammonium/ammonia somehow seems to be a big mystery. At lectures and training courses all over the world, I repeatedly experience the strangest views on these two nitrogen compounds. First the facts: Ammonium NH4 is non-toxic to fish. At pH values above 6.0, an increasing amount is converted to toxic ammonia (NH3) as the pH value increases. Normally, nitrifying bacteria in the pond water and especially in the substrate and filter convert the ammonium directly into nitrite (NO2) and further into nitrate (NO3). The danger of the bacteria no longer being able to break down the ammonium only occurs when there is too much of it (too many fish, overfeeding, too small a filter). Then there is an "ammonium gridlock“ and the value rises into dangerous ranges if the pH value is above 6.0. Every fish releases a large amount of ammonium directly into the water through its gills every day. This ammonium must also be converted by the bacteria via nitrite to nitrate. Thus, even without overstocking and overfeeding, a large amount of ammonium is released into the water. Unfortunately, many ammonium/ammonia tests are somewhat peculiar: The colour chart enclosed for reading out the value has ammonium/ammonia in the heading. The user is thus allowed to choose what his result now shows! Also missing is a table for reading out how much ammonium turns into toxic ammonia depending on the pH value. Such tests are really not well thought through. A great pity and indeed dangerous for the users and their koi!
5. Add salt to your pond from time to time – it's good for the pond and your koi!
There are certainly pond owners who have had good experiences with salt additions, but which ones exactly? Adding salt definitely has the following effect: Bacteria (both good and bad) cannot tolerate changes in the salinity of the water and perish. This is good when it comes to pathogenic germs, but extremely problematic when it comes to the important filter bacteria! This has been clearly proven scientifically. In the koi pond there are usually only a few plants, in garden ponds considerably more. Plants, like algae, do not like salt either. Salt has an important therapeutic purpose: by increasing the salt content we change the osmotic conditions in the water. Normally, fresh water flows permanently into the fish (water always diffuses through the semi-permeable cell membranes in the direction of the higher salt concentration to create a concentration balance). By adding salt, we reverse the conditions: The fish releases water into the now salty water and also releases slime in the process. Parasites often sit in or on the mucous membrane. For disease control, adding salt makes perfect sense. But not permanently! The disadvantages clearly outweigh the benefits. And by the way, neither the general hardness GH nor the carbonate hardness KH is increased, because sodium chloride (NaCl = table salt) contains neither the one nor the other.
6. You can really save money on food! There are big bags of food for little money on the internet
Dear koi enthusiast: You may have spent a lot of money on your koi and love your fish like family members. Do you really want to save money on food? Would you also pour multigrade oil from the discounter into your well-kept Porsche?
Let's take a technical approach: Food can look the same but have serious differences in content. The big cheap bags of food often contain fattening food for carps or even worse: for trouts. Trouts are predators and need a completely different composition than our koi, which are omnivores. Carp fattening food is not really suitable either. Unless you find roly-poly koi attractive. These foods have unsuitable protein/fat ratios that will lead to unattractive body shapes and deficiency symptoms. The correct protein/fat ratios depend on the water temperature: between 5-15 °C 2:1 would be correct ( winter food). In spring and autumn at 10-20 °C a protein/fat ratio of 3:1 is correct and in summer at high temperatures a 4:1 ratio should be aimed for.
With an inappropriate feed composition, the following happens: The fish cannot digest the food properly => it may remain in the digestive tract for too long (e.g. in winter) and lead to massive problems or even death. If the protein/fat ratio is wrong, the koi's organs become fatty and their resistance to disease decreases. Inferior ingredients (= low price) lead to increased excretions. By the way, every dog owner knows this! High-quality food can be digested better and less is excreted. As a result, the animals with LESS food become stronger and also burden the water significantly less due to fewer excretions. Please think again about whether you should perhaps go for a higher quality food. Your fish will thank you for it!
7. It’s no problem to switch off your pond filter at night!
It all comes back to the subject of money saving. Why else would we want to turn off a filter? If you turn off your filter or if it has been idle due to a prolonged power outage, the oxygen content inside the filter drops dramatically. The bacteria die or switch over their metabolism. Toxic metabolic products such as hydrogen sulphide (H2S) are often produced. When the power is then switched on again, this wonderful mixture of toxins and dead bacteria is flushed into your pond. Your fish will not be very pleased. By the way, a completely new problem arises: a previously colonised filter material is very difficult to repopulate! It may take many weeks before your filter starts up biologically again! Therefore, please let your filter run continuously and clean it if it has been idle for more than 12 hours.
8. Sludge at the bottom is natural and good for the pond!
Only your frogs, toads and newts will be happy about a hefty layer of sludge at the bottom of your pond. And yes, sludge is natural. Unfortunately, ALL natural ponds and lakes silt up in the course of their lives due to leaf input. The leaf layer unfortunately only brings disadvantages for us koi pond owners. It considerably reduces the water volume and the swimming space. Use a folding rule to measure the depth at which your sludge layer begins. Don't be surprised if only half of the water column is left after many years! Organic matter such as leaves and dead algae are biodegraded by bacteria and microorganisms. This is nice and seems always positive, but these processes devour vast amounts of oxygen. At the bottom, oxygen levels can even be so low that small animals die and the degradation processes come to a standstill. Mechanical sludge removal (please arrange it in portions over a period of weeks) and a biological sludge remover together with vigorous aeration are absolutely sensible!
9. Build your pond in a nice sunny spot in your garden!
Sun always sounds good – just not for your pond. There is nothing at all wrong with your pond getting sunlight, but please not the whole pond or 12 hours a day. Partial shading or even a sun sail are basic requirements. In summer, water temperatures can rise to uncomfortably high levels. Even 2 m deep koi ponds can become too warm, as all water layers are mixed together by bottom drains. Higher water temperatures cause the oxygen content to drop drastically. The maximum amount of O2, for example, drops from 11 mg/l at 10 °C to only 7 mg/l at 35 °C! The oxygen requirement of your koi is exactly the opposite: At 10 °C it needs 45 mg/l O2 per kg fish per hour. At 20 °C the oxygen requirement doubles to 90 mg/l and when feeding it rises to 500 mg/l (at 20 °C)! Therefore, even a good summer food should only be fed sparingly at water temperatures above 30°C. Pond aeration is not only sensible as mentioned in point 8, but absolutely necessary in the hot season! A watercourse, water spouts, a small waterfall and the like are of course also aeration options.
10. If you have algae problems, you must eliminate nitrates AND phosphates from your pond!
Nitrates and phosphates are indisputably the main nutrients for algae. If you place a canister of distilled water in the blazing sun, no algae will form in it, despite the enormous amount of light. Nutrients are the cause of algae - the light is only the motor that then accelerates the algae formation.
Some smart biologists have discovered that we can save ourselves some of the removal. And we are back to our favourite topic. You can choose one of the two nutrients! Algae depend on a certain ratio of the two nutrients to each other (“Redfield ratio” for your Google search). Since phosphates are easier to control with good phosphate removers than nitrates, I recommend phosphate removal. You often have the choice between a liquid product and a substrate for your filter, and I always recommend the latter. The liquid PO4 removers precipitate the phosphate and it sinks to the bottom. How are we supposed to get it out of there? Filter cleaning is much easier. And if your algae no longer have phosphates available, they will decrease visibly. Starvation isn’t good for growth!
Does all this sound complicated? Don't worry, it only sounds that way. Pond care and healthy koi are not rocket science and are not reserved for the absolute experts. With common sense, some time commitment, a little expertise and a willingness not to always buy the cheapest, your fish will come through all the seasons healthy and lively. And that's the most important thing, isn't it?