some things required for filtration/cycling to be successful are.. good ph/kh, if the ph is too low it can cause the cycle to stall, never let it go below 7 try to keep it at 7.4 - 7.6, good kh will buffer the water and prevent ph from dropping. use bicarbonate of soda to increase ph/kh
good temperature, aerobic bacteria (the one that consume/convert ammonia/nitrite) prefer warm water, when cycling use a heater to encourage growth, never let the temperature drop below 10°c as this will stunt growth.
good oxygenation, this is very important as it is required by both the animals place in the aquarium and the filter bacteria, filter bacteria use the oxygen to convert/consume the ammonia/nitrites, always use air stones in the aquarium even if a air-sponge filter is fitted, air sponges produce large bubbles which give low dissolved oxygen compared to small/fine bubbles.
now for the filtration itself, there are three most used parts of filtration.. mechanical, biological, chemical.
mechanical filtration is sponges/brushes and anything that is used to trap muck/debris,.
biological filtration is high porous rocks/plastic beads/ceramic balls/rings anything that can be used to house bacteria.
chemical filtration is activated carbon/zeolite anything that can be used to remove chemicals from water.
there is also the water treatment category for filtration aswell, this include UV light or anything that is used to kill bacteria/algae/pathogens.
last but not least natural filtration, this includes plants to remove nitrogen compounds from the water, invertebrates etc.. which remove muck/debris.
sponges are good for catching debris/muck but are inefficient for bacterial and chemical filtration. sponges have low surface area so although some bacteria can inhabit the sponge there won't be as many as with bio-media, because of the low surface area only a reduced amount of chemicals can be absorbed/trapped.
bio-media are good for breeding bacteria and removing most nitrogen compounds but are inefficient for mechanical and chemical filtration. because of the compacted surface area flow through is reduced so the muck/debris is only trapped caught on the outer surface, to be used as chemical filtration would damage the bacteria colony.
chemical filtration is good for removing some toxic compounds but is inefficient for mechanical and biological filtration.
as to the media itself, mechnical shouldn't need replacing for the life of the tank unless degrading, just wash by squeezing flush through with old tank water, bio-media shouldn't need replacing for the life of the tank unless degrading, just wash using old tank water, chemical filtration should be replaced monthly as it becomes ineffective, although some like zeolite can be re-energised it is cheap enough just to replace.
now some things about ammonia, the ammonia that is tested is called TAN (total ammonia nitrogen) this is made up from free-ammonia (toxic) and ammonium (non-toxic), ammonium is the base compound with free-ammonia being a bi-product, the speed at which ammonium breaks down into free-ammonia depends on three things.. ph, temperature, salinity.
the higher the ph the more free-ammonia is produced and vice versa, the same applies to temperature.
salinity is reversed, the higher the salinity the lower the free-ammonia.
the aerobic bacteria that colonises the filter use the free-ammonia as food and convert it to to nitrites, they have great difficulty consuming/converting ammonium.
if you suddenly get a spike of ammonia ie.. 1ppm the first reaction is to panic... don't, 1ppm ammonia is 1ppm TAN, test the ph and temperature.
for example 1ppm at 7ph at 15°c is 0.0026ppm free-ammonia which is very safe levels (0 - 0.025 is safe, 0.025 - 0.05 is warning/harmful, 0.5 + is deadly)
the same 1ppm at 8ph and 20°c is now at 0.037ppm which is harmful.
for ammonia calculator go here..
Free Ammonia Calculator
for toxicity levels go here...
Your Guide to Ammonia Toxicity - Aquarium Advice - Aquarium Forum Community
nitrites are harmful at any levels and should be dealt with.
nitrates although not as harmful encourage algae growth, high levels in an established tank is a sign of poor husbandry, a bit like swimming in sewage.
oh and always use a type of holfreters solution in the water containing an axolotl, holfreters makes the water more comfortable/suitable, it help prevent and cures fungul issues, it works as a shield against ammonia/nitrites .. info here..
Axolotls - Requirements & Water Conditions in Captivity
yes I know this was quite long winded
