Decomposition of food in SW aquariums

ORP stands for Oxidative reductive potential, this is how oxidative or reductive your water is and is determined by the type of chemicals in the water, it does not necessarily regulate how fast your bacteria can breakdown organic material. What will determine how fast microorganisms can breakdown organic waste in your system will include; what specific microorganism species are in the system, temperature, type and amount of waste, and the amount of available oxygen.

The enzymes and acids produced by bacteria and fungi, respiration by microorganisms, fish and other organisms have a reductive effect on their environment, oxygenation from protein skimmers, photosynthesis, use of ozone and good circulation will have an oxidative effect.

The main decomposers of uneaten food and faeces are bacteria and fungi. For the bacteria side of things, there are many bacteria and tend to get lumped into how they feed and what they feed on. The main bacteria involved in the breakdown of uneaten food or faeces is done by organic bacteria and inorganic bacteria. The first bacteria I'll mention are the organic heterotrophic bacteria (this means that they can't produce their own food, they produce enzymes and acids that can digest organic material for food). This type of bacteria breakdown the organic material (composed mainly of protein, lipids(fats) and carbohydrate) using oxygen, during the breakdown hydrophobic (water hating) molecules (like the lipids) will be released and float to the surface causing surface film, one exit route for this will be via your protein skimmer, organic bacteria will also break the lipids down. When proteins get broken down some ammonia is produced as a by-product, this is then broken down by chemoautotrophic bacteria.

These chemoautotrophic bacteria are inorganic nitrifying bacteria and oxidise ammonia (NH4) (which is inorganic) to nitrite (NO2) and then to nitrate (NO3). Other organisms excrete ammonia directly as a waste product, some can excrete ammonia in significant amounts including shrimp and fish. Ammonia is very toxic to aquatic life at low levels, nitrite isn’t as toxic and nitrate has to be at very high levels to cause short term (acute) toxicity. Significant amounts of nitrate have been found to cause problems with aquatic organisms in the long term.

Nitrate and nitrite can be broken down by denitrifying bacteria, these are heterotrophic organic bacteria. Some require a completely anoxic (no oxygen) environment, others prefer a suboxic (some oxygen) and even oxic (fully oxygenated) environment. Nitrate is broken down to nitrite and then to nitrous oxide, then to nitrogen gas. These bacteria require a food source in the form of organic carbon and phosphate, they then use nitrate or nitrite as an oxygen source utilising the oxygen molecule from these compounds (NO2 and NO3 respectfully). In an anoxic environment these bacteria break down nitrate and nitrite all the way to nitrogen as they need all the oxygen they can get, in an suboxic/oxic environment they just break nitrate and nitrite down to nitrous oxide and can do this very quickly.

In anoxic environments sulphate reducing bacteria can grow and use sulphate as an oxygen source to break down organic carbon and phosphate as a food source, but precipitate sulphite (sulphite has been associated with black dusting) and produce hydrogen sulphide (it smells eggy) which is toxic in small amounts.

Fungi have a very similar feeding strategy as heterotrophic organic bacteria, they can also live in anoxic, suboxic and oxic conditions, they can produce enzymes to break down organic molecules. They can also produce scary mycotoxins byproducts which are disease causing and can be toxic.

Okay, I think I think I have well and truly started the discussion you wanted, I hope I have answered some of your questions.

P.s. I feed my fish a small amount twice a day, IMO working out how much to feed will depend on what species you want to keep and their needs.

 

WOW lots of great responses while I was at work. Thanks everyone.

I'm planning on checking out Reefcleaners ASAP. I wasn't familiar with them until a few days ago. Do livestock sent from them fare well being sent via mail, Fedex, UPS, etc?

OK so my fish are now only getting fed 2 times per week. REALLY glad I was set straight on this. It's interesting how different people have their own schedules (a few small meals daily, once daily, 2 times a week, etc.). Glad to see everyone has success with their method.

 

the amount of freebies included more than makes up for any die off in the bag. there is very little IME anyway though

 

Freebies???

 

You order 35 snails, they send quite a few more in order to make sure you get 35 snails that survive.

 

Got it, thanks. Just sent them a request for a cleanup crew quote.