My water has gone green. What should I do?

Normally a problem in the first weeks of setting up a new system. This is suspended algae we are talking about, if you were to dip a glass into your fish tank and fill it with water then hold it up, the water looks very green and is hard to see through it. This is a natural phase your system will go through as cycling happens. Pump full time if you aren’t already. Stop all feeding, any nutrient going into the system will only feed the algal bloom. If possible cover the top of your fish tank to keep light away from the water.

The sides and bottom of my tank is covered with green slime, should I clean it off?

No, this is biofilm and we don’t recommend that you take this off, generally it only grows as a thin layer on the surface of your tank, it causes no harm to the fish or the system in any way and it helps by harbouring the beneficial bacteria. Many species of fish may peck at the biofilm on the sides of the tank, eating it.

I have long strands of algae growing in my tank, what should I do?

Stringy or filamentous algae, not very nice and it can start to take over your fish tank with its long strands of algae. Try to keep the light off the water if you can by covering the tank. Remove what you can from the sides of the tank manually. Perhaps add some known algae eaters to the tank if you can. We added a few yabbies to one of our tanks which had filamentous algae, they have cleaned it up nicely.

How long can I leave my fish without feeding them?

Almost all species of fish will live happily for weeks without feeding. If you are going away on holiday for a week or two, we would recommend that you get a friend family member or neighbour to come around once or twice a week to check your system and feed your fish. If this is not possible, then leaving the fish without feed for a week or two will not cause any major problems. I would rather leave them without feed than have an automated feeding method because if they are off the feed for some reason, the automated feeder will keep dumping it into the system and it may foul the water.

My fish appear unwell, gasping at the surface or showing labouring breathing, or erratic behaviour, perhaps flashing?

If your system is pumping on a timed cycle increase the pumping to 100% of the time, if your system has not been salted before, salt your system water. Using pool salt, salt your system to 3ppt, this means in 1000L of water you would add 3kg of salt. Salt aids fish health and at these levels most plants will remain unaffected, however some plants like strawberries may suffer.

My fish are off their feed, what should I do?

If it’s only been a day or two, don’t panic. Think about things: what sort of fish do you have? What are their ideal conditions and what are your water temperatures? How long have they been in the system? Fish can often take a few weeks to settle into a new home. Stand back and throw just a few pellets at a time, they might be shy, then come back in a while and check if they have eaten them.

How much should I feed my fish?

As much as they want to eat if your system is cycled and all is well. You will find that different species have different personalities. Some fish, like trout are eating machines, throw a handful of feed into your fish tank and they will go crazy leaping out of the water. They seem to have an almost insatiable appetite. Other species are shyer and will eat more cautiously. Once your system is established, the simple rule of thumb is to feed them as much as they want to eat within a few minutes. Throw a small handful of feed in, if they eat it all, throw some more in, and so on. When they start slowing down and don’t appear to be so hungry, stop feeding them. Some fish are happy to eat all day long, others may prefer to eat at certain times of the day. You can tend to train the fish, if you have been feeding them every day when you get home from work, then don’t be surprised if they don’t eat when you decide to feed them in the morning for a change.

What sized pump do I need for my system?

A question often asked! A general rule of thumb that can be applied is that you want to turn over the fish tank volume once an hour. So, say you have designed a system using a couple of IBC’s, you have a 1000L IBC fish tank and two growbeds above the fish tank made from the other IBC. Firstly you need to know roughly what head your pump will be pumping to, this is the height from the surface of the water where the pump is, up to the highest point it will be pushing the water. Say for this example it might be about 70cm from water surface in the fish tank to the top of the growbeds where the water inlet is. So you will want a pump that can pump at least 1000L litres/hour at a head of 70cm. If you check out pump boxes then you will notice that most of them have a graph comparing pumping rates at different heads. Personally I tend to go a little more because this allows for future expansion and changes, or extra plumbing if required at some stage. Remember that if a pump says it’s flow rate is say 2000L/h, that is at 0 head, with no restrictions from pipes and fittings.

What fish can I grow in my system?

That’s going to depend totally on your location. Major factors are, relevant government agencies or bodies and what they allow in your area, you might have a fishing and gaming or agricultural department you can check with. The next factor is climate, I really recommend growing a fish which will be happy at the natural temperatures of your system without requiring external heating and or cooling. I have seen some elaborate attempts over the years at heating and cooling water to keep a particular species of fish, in reality they don’t tend to last long term because of the expense or effort in maintaining optimum temperatures for the particular species. If you live in England, don’t try and grow Tilapia, you can grow them, but you need to keep the water temperatures elevated year round. Grow trout, they will grow year round without any heating.

My pH is high or low what should I do?

There are a few things you can do, however always remember little and often rather than large changes. After running aquaponic systems for well over 10 years, I have never adjusted my pH in any of my systems. Here at the display centre we recently tested some of our systems and found that a few of them had a pH down around 5.5 which is considered to be very low. In fact in a lot of literature may tell you that nitrification will stop at levels below 6, we’ve found this to not be true. Some fish species don’t like low pH, other species are quite happy at a low pH, it might be worth checking your own fish species to find out if they are ok. The plants are certainly happy at a lower pH and more elements are available at low pH. High pH is generally more of a problem than low, high pH means that ammonia is more toxic to fish and that many micronutrients are locked up and not available to plants. pH naturally comes down in an aquaponic system and generally people are trying to find ways of keeping the pH up. If your pH is high you need to look at a few things, check the water you are using to top up your system. If it has a high pH find another water source for a while. If it’s not your top up water perhaps it’s your media in the growbeds, test your media with the vinegar test. Whatever your pH reading is, remember “don’t panic”. This is especially true during the early stages of an aquaponic system, during cycling and for a while after, perhaps the first 6 months of operation, you can experience some swings in pH, just let the system settle and mature, if you have checked your media and top up water and they are fine, just leave your system to do its thing.

My ammonia/nitrites/nitrate levels are high, what should I do?

Firstly, if it’s your nitrates, don’t panic these aren’t highly toxic to fish, you need to think about planting some more plants to use up the nitrates. If it’s Ammonia or nitrites, there are a few things you should do. Number one thing, STOP FEEDING. Secondly look for uneaten feed on the bottom of your tank and remove any that you find. If you aren’t already pumping full time, turn the water pump on 24/7 for at least a few days, salt the system (to 1ppt), this will aid your fish if the nitrite levels are high.

My ammonia/nitrites/nitrate levels are low or nonexistent, what should I do?

Be happy! 🙂 Many of the systems we run at the display centre here show levels of 0 for all of the above, the systems are producing well, all nutrients are being converted, and also the plants aren’t being force fed to any extent by having constant levels of nitrates in the water.

Do fish need sunlight?

No not at all, or at least only in very small amounts, ultimately it’s great if you can keep the sun off your fish tank, fish are happy when they feel protected and in the shadows, there aren’t many fish that like sitting in the sunshine. This has come about through many generations of breeding, those sitting out in the sun would be picked off quickly by predators from in the water or the sky. Happy fish are fish that aren’t stressed so they will be less susceptible to disease and they will eat more and put on weight quicker.

Can I put plants and other features into my fish tank?

It’s recommended that you keep your tank as free as possible of objects if you want to keep maximum numbers of fish. The more things in your fish tank, the more places there are for solids to catch and build up. We sometimes put in a couple of short sections of pipe in the bottom of the fish tank for crustaceans to hide in to give them protection from the fish. Pot plants like water lilies, lotus plants, Chinese water chestnuts etc may be attacked by either fish or any crustaceans in your tank. If you have low stocking levels or the right species of fish you may be ok. Floating plants can work very well in a system and they have been talked about previously in the plant section of this manual.

Do I need an air pump for my system?

Probably not, this will depend on a number of aspects of your system. We have found that in all of our systems the water splashing back into the fish tank creates enough dissolved oxygen in the water for the fish of a fully stocked system at the recommended stocking levels. A little extra air certainly doesn’t go astray, but there is no reason to get a huge air pump with lots of air stones for your IBC system.

I have algae on my growbed media, what should I do?

You need to look at a couple of things, do you have water going out over the top of your media where the sun can hit it? This will cause algae to grow. Best if you can try and make sure the water goes straight down into the media away from the sunlight. Another way to help this problem is to put some worms into your growbed, composting worms help consume uneaten food, algae and old dead root matter within the growbed.