Ammonia Poisoning

• Lethargy
• Hovering motionless at the bottom of the aquarium
• Red gills
• Lack of appetite

• Bleeding gills
• External and/or internal bleeding

To remedy such a situation, you can conduct a water change (25-50%), attempt to lower the pH through means such as commercial chemical pH adjusters, chemical filtration. For long term solutions, you can use reverse osmosis (RO) or deionized (DI) water when conducting water changes.

Nitrite Poisoning

While not as toxic as Ammonia Poisoning, it is still deadly to fishes, especially in high doses or over long periods of time. Most symptoms, causes and treatments are similar to that of Ammonia Poisoning, with fish gasping for air at the water surface being another possible sign of nitrite poisoning.

Other than the common solutions in 'Recognising Complications', you can attempt 1 teaspoon of salt per 300 Gallons of water to help the fish to cope with nitrite toxins.

Carbon Dioxide Poisoning

This occurs when CO2 levels are in excess of 25-30 ppm, which is when it becomes dangerous for fish, which could lead to suffocation.

• Rapid breathing
• Gasping for air
• Staggering swimming behaviour

Causes could be caused by the malfunction of the CO2 reactor, lack of plants, or the inability of plants to absorb CO2 if the lighting is insufficient.

One solution is to heavily aerate the tank through surface agitation and air-stones. This will cause the CO2 to dissipate from the water resolving the complication.

Hydrogen Sulfite Poisoning

This happens rarely, usually when there is a severe lack of maintenance or an extended power outage, the malfunction of equipment could lead to hydrogen sulphite forming in the gravel or within the filter. Hydrogen sulfite transforms iron within the blood cells into sulphide which will lead to suffocation of the fish.

Symptoms are similar to those of ammonia and nitrite poisoning, while also including a possible rotten egg like stench. The most important part of this is prevention, which means that cleaning is key in this regard. The gravel should be cleaned regularly and the filter has to be rinsed out well, in the case of a power outage, before restarting it.

Chlorine, Chloramine, Heavy Metal Poisoning

These complications are usually not a problem, due to the fact that water usually is treated with a conditioner prior to use. These chemicals are typically added to tap water to make it safe for human use, but they irritate the gills and block the oxygen carrying cells, leading to suffocation in fish. If Chlorine or Chloramine poisoning occurs, a chlorine odour can be detected alongside the fish gasping for air, Some medications and aquarium additives contain copper. As such these should be used with caution and you should ensure that they are not used over an extended period of time.

Solutions for this problem include adding a water conditioner as soon as possible, as chlorine/chloramine can kill all fish within 24 hours. A high concentration of heavy metals can lead to abrupt death without warning signs. A good water conditioner will also remove heavy metals, alongside chlorine and chloramine.