Water Chemistry - Part 1

Water Chemistry – Part 1

Hello. A while back I wrote one of these blogs talking about setting up a new tank; and in that I briefly skimmed over some water chemistry and said that it deserved its own blog. So, welcome to that blog, or at least the first half of that blog. 

Owning fish, be it in a pond or tank, involves a lot more chemistry than biology. We often say that what you’re actually looking after is the water, if the water is good the fish will mostly look after itself, although feeding and cleaning is still a good idea. Over these two blogs I’m going to go over the six most common aspects of water chemistry in relation to keeping fish: pH, KH, GH, Ammonia, Nitrite, and Nitrate. Starting with pH, KH, and GH. I’ll cover what each of them means, why they’re important, what they should be, and how to fix them if they go wrong. So do bear with me, I’ll do my best to make it digestible; but water chemistry is a bit of a dry topic, ironically.

pH

pH is a measure of how acidic or alkaline the water is. This is expressed from 0 to 14, where 0 is the most acidic, 14 is the most alkaline, and 7 in the middle is neutral. The pH scale is what’s called a logarithmic scale, there’s no need to go into the mathematics of how that works, but what it means is that a pH of 9 is 10 times more alkaline than 8, and 100 times more alkaline than 7, 1000 times more than 6, and so on. So, while something going wrong with the water pH might only look like a small change, it really isn’t. The pH should be kept as stable as possible, even if it’s fluctuating within the pH tolerance of the fish, it’s the fluctuation itself the fish won’t like. Fish are sensitive to change; even a change from bad to good will cause upset if it occurs too quickly. Most aquaria are going to be aiming for a neutral pH of 7 as most of the common species of fish found in the aquatic trade will be happy with neutral water, whereas ponds tend to be better off with a pH of 7.5 - 8. There are of course exceptions that prefer the pH be greatly one way or the other. For example, the ever dramatic (in every sense of the word) discus fish prefer a pH of 5 - 6.5, while the recommended pH for African cichlids from the lakes in the Great Rift Vally can range from 7.8 - 9.

The pH being too high or too low for a species will likely result in alkalosis or acidosis respectively. Symptoms of both of these include, lethargy, jumping, excess mucus production, browning of the gills, and gasping for air. Alkalosis can also cause reddening of the skin and burns. The only way to cure it is to correct the pH. Up in t’ North, or at least here in the North West, our water tends to be quite soft and acidic, usually pH 6.5-7, as the majority of it comes from rivers and reservoirs, meaning we often have to use KH buffer to increase the pH and keep our water stable, preventing pH crashes from occurring after a couple of water changes. This also means that lowering the pH if necessary isn’t an issue, as a partial water change as part of our regular tank maintenance will often do just that. However other areas such as down South in West Sussex, water tends to be hard and alkaline due to the majority of water being drawn up from underground chalk aquafers which are very mineral rich, leading to a pH as high as 9 in some areas. This can be brought down using chemical solutions that neutralise carbonate hardness (KH) or more natural methods like the tannic acid from decorative wood, peat moss and almond leaves. Regular testing of pH should be carried out to ensure that it isn’t fluctuating, or outside of desired parameters. In store we use NT Labs chemical tests, of which pH is certainly the least complicated, just add five drops of the testing solution to a 5ml water sample, give it a quick shake, and compare the colour of the sample to the colour chart provided. Easy as that.

KH

KH (Carbonate Hardness) is a measure of minerals in the water that effect the pH, specifically carbonate and bicarbonate ions, often measured in °dKH (degrees of carbonate hardness) or ppm (parts per million). KH is what we’d call a buffer, it directly affects the pH and keeps it stable if maintained, which is an essential aspect of fish keeping as stability is very important. Fluctuations cause a great deal of stress to fish and will often result in illness and/or death. But the amount of KH in the water is always dropping, its minerals being used up or neutralised in many of the systems natural processes, such as the respiration of the fish and filter bacteria, and growth of plants. Water changes in soft water areas and rain will also lower the KH. The more fish you have and the bigger the filter, the faster it will decrease. For example, here in the shop in spring when our pond vats are at their most heavily stocked and we’re getting the filters back up to full working capability, we have to buffer as often as three times a week. This is something to be on the lookout for when starting a new tank or pond too, as the newly developing filter bacteria will likely bloom and cause the KH to drop rapidly; possibly crashing the pH if not rectified. Good news is if you live in hard water area; dropping KH is not likely to be an issue for you, every water change will replenish some KH so it might not drop low enough to lower the pH in between water changes. Good news for soft water areas; it’s easy to fix and keep on top of. Best way to keep on top of it is regular water testing (you’ll have read those words a lot by the end of these two blogs), which enables you to acknowledge when your KH needs topping up before it becomes an issue. For most general community tropical tanks, a KH of around 4-8°dKH is considered suitable, for ponds we’d recommend around about 5-8°dKH. With the NT Labs KH test you count the number of drops of KH testing solution it takes to turn a 5ml sample from blue to yellow, with every drop, including the first, being 1°dKH. Like with pH, always be mindful of any specific requirements of KH your fish may need if you’re thinking of getting something a little more specialist. 

KH buffer usually comes as a powder and the amount you need to use will differ depending on brand, so always follow the dosage guide that comes with it or ask a member of staff at the shop if you’re unsure. Whenever we do a test for someone here, we’ll work out exactly how much buffer you’re going to need. There are other methods of raising the pH, such as adding crushed coral, oyster shells or ocean rock but these are more of a slow release of KH over a period of time as the mineral dissolves into the water, and personally I prefer something I can measure and get exactly right for what I require, not something you can do with natural materials like that. Lowering KH is more difficult and likely to cause issues with pH if done incorrectly, wood, peat moss, and almond leaves are the natural options here, but chemical products that lower pH are available, once again follow the manufacturer guidelines when using these. Another way to lower KH is with a partial water change (this is the only time you will hear us recommend that), soft water areas can likely just use their water as normal, while hard water areas might consider using RO (Reverse Osmosis) water. Long story short, RO water is water that has been processed by an RO filter, removing somewhere around 99% of impurities, including KH. Perform a water change with RO water, testing as you go, and it should be relatively easy to lower the KH to where you want it. Most aquatic retailers, including ourselves, will sell RO water. 

GH

GH (General Hardness) is very similar to KH in a lot of ways, but the main difference that matters to us is that it has no effect on the pH. GH is often measured in °dGH (degrees of general hardness) or ppm (parts per million). Specifically, it is a measure of magnesium and calcium ions. Both of these minerals are important for growth in a healthy aquatic system, for example magnesium is essential to the process of photosynthesis in plants, and the function of muscles and nerves, while calcium is used in the growth of bones, scales, and the cell wall of plant cells. This all sounds like a win win situation, but of course you can have too much of a good thing. Too much GH in the water can affect a fish’s osmoregulation, the biological process of controlling the intake and loss of water from the fish’s body. I’m not going to go into the biology of how or why, but it’s enough to know that too much GH can affect water concentration making osmoregulation more difficult for the fish, possibly leading to stress, illness, and death. Too little GH can lead to developmental issues resulting in stunted growth and reduced lifespan. Like KH, GH will drop over time but much more slowly. Check GH with regular water testing to ensure that it remains at the concentration it’s supposed to. For most general community tropical tanks and ponds, a GH of around 4-12°dKH is good. As with the KH, a GH test involves counting drops until a colour change again, two drops of one solution into a 5ml sample will turn it a dark red, count how many drops of a second solution it takes to turn it blue, every drop is 1°dGH.

Raising and lowering GH can mostly be carried out using the same means as KH. Raise it using GH buffer, some buffers will do both KH and GH, or you can use crushed coral, oyster shells or ocean rock, they’ll raise both KH and GH too. Lowering GH is pretty much just a case of partial water changes and testing (turns out, there’s two times you’d hear us recommend that), again RO water can be used as with KH.

Right, that should do for this one. We’ll leave it there before you fall asleep from boredom.

Next time I’ll be covering what’s going on inside your filter, the nitrogen cycle. 

Thanks for reading.

Nathan.