The Spring Pond

Today we are really pleased to bring you our first guest blog from a fellow member of the Derby and District Aquarist Society, Keith Jackson.  He will be taking us through his experience of The Spring Pond.  

Keith is a retired engineer who has been keeping tropical fish for 40 years and a pond for 11. His first love is the South American family of small catfishes of the group Corydoradinae, covering the genera Corydoras, Brochis, Scleromystax and Aspidoras.  He has promised us a future piece on this subject.

From Keith:

After a particularly cold Winter, my pond is emerging quickly, just as the Spring bulbs have rushed into spectacular flower in our garden. Although things have been delayed this year, Mother Nature is doing her best to get back on schedule.

My pond is about 2m deep and 2.5m in diameter, about 2,000 gallons or 9,000 litres in capacity, and I inherited it when we moved to this house in 2002. I keep mostly koi but there are a few goldfish remaining from when I first set it up again. Not that the goldfish are particularly overawed by the koi as they are pushing  30cm body length and seeing the colours and flowing fins of Sarasa Comets moving around certainly adds to the spectacle, even though I probably wouldn’t include them if I started again today.

Around this time of year, most pond-keepers will have an outbreak of algae. It may arrive as green water so opaque the fish are like ghosts or as long strands that make swimming difficult and get entangled in pumps or, indeed, as any combination in between. Sometimes the growth of the algae is incredible and the keeper can easily despair of getting rid of it and he or she tries to remove it physically. It seems like a never-ending task. So what causes such outbreaks? That’s simple. The presence of chemicals that the algae can feed on, which leads us to what’s often called the Nitrogen Cycle.

All fish eat and excrete but fish, unlike humans, release Ammonia as their liquid waste. When you think about the waters fish come from, whether it’s a lake, stream, river or the sea, the volume of water is huge or it is flowing quickly enough that the fishes’ waste products are diluted rapidly and the fish don’t suffer. A limited, static volume of water, like a tank or pond, is quite a different story and we all keep a much greater density of fish per unit volume that would be natural in the wild. Ammonia is highly toxic to fish and it is the reason so many new fish-keepers, given bad advice by shops more interested in profits than the welfare of the animals, give up when they lose their fish in no time. So what can we do?

It would be very difficult and expensive to simply flush the ammonia away so we use a filter and hope that it will develop the bacterial cultures we need to keep our fish safe. These cultures take time to reach an optimum level and the development time is the reason responsible shop-keepers only allow newcomers to add fish gradually to the new aquarium or pond. There are two groups of bacteria involved. One uses ammonia as a food source and releases nitrite compounds and the second takes that nitrite and releases nitrates. All three are toxic to fish but the relative toxicity reduces along the cycle so fish can tolerate far higher concentrations of nitrates than ammonia. Nevertheless, nitrates are toxic and regular water changes are vital to keep your fish in the best of health. That and the use of a test kit so you can see how well your filters are coping. Once established, you should find no ammonia, trace amounts of nitrite and some nitrate. If the numbers are suddenly different then you know there is a problem to be traced and fixed.

Any gardener knows that nitrates are commonly used as fertilisers and algae are aquatic plants that enjoy nitrates every bit as much as your prize flowers and vegetables. That’s why algae appear in ponds in Spring: there is food available to them and an environmental niche to be colonised. To minimise this problem there are a number of things we can do:

Routine maintenance. Once the weather starts to warm up and the fish become active I restart my weekly water-changes – about 5% - and clean out the brush chamber of my filter. I always check the pump is clear of any algae strands or dead leaves so the flow around the system is kept up.

Feeding. The best tool for an aquarist or pond-keepers is their eyesight. Get to know the normal behaviour of the fish so you can quickly see if any are unwell. If you feed them, are they eager to take it or do they peck at it and leave the rest? If it’s the first you can feed them again later. If it’s the second they’re not yet ready to take the amount you’re giving so reduce it until they do take it eagerly and then build up the amount gradually.

Ultra-violet Lamp. Algae that cause green water are killed by ultra-violet light but you need enough power to kill the algae passing through the system. For my pond, I found a 33W lamp was too small and now use a 55W instead and I leave it switched on all the time, even in Winter. Tubes should be replaced every Spring as their output declines and they will be less effective in Year Two.

 Green water is not a problem for fish. They will strain the tiny particles of algae out using their gills and eat it. We buy it, as spirulina, as an additive in fish food!  But if we want to see our babies we need to deal with it.

Algicides. There are a number of potential problems with algicides, not least because they are not
equally effective against the hundreds of possible species that we can find in our ponds. One that might work one year may not the next because it’s a different alga. It might kill off the dominant type but not be able to do the same to the species that takes over the niche a couple of weeks later. We always have a fight on our hands!

      So is there an answer?

      Basically, you need to minimise the amount of nitrates available to the algae. In other words, the best way to getrid of it is to starve it. I am lucky to have a waterfall into which I can put water-tolerant plants, such as the water grass Glyceria and the Mimulus or Monkey Musk flowering perennial, and they take up a lot of nitrates themselves. The problem with simply relying on that is that the higher plants start to grow well after the algae can get going so I use an algicide based on extract of barley straw to control the algae until the plants take hold and keep things in balance naturally.

      If your pond doesn’t allow you to use plants as a vegetable filter, you will need to keep the nitrates in check by changing more water and testing the water regularly to make sure you keep things in balance. At the end of the day, fish are a responsibility, just as much as a cat, dog or budgie, and we owe it to them to keep them safe and sound. Do it well enough and they might even spawn for you. You never know!

     

      Keith