High water turnover - discuss :)

[Wolfenrook]

I can see the merits in both methods, and at the end of the day our aim is to combine good circulation with large biological capacity is it not?

Now Clive argues that this is best achieved by using a filter with a high flow rate, in my experience this is not always the case however, there are a lot of external filters out there with really powerful pumps but absolutely tiny capacities! My last filter for example! It was a Sicce Genio2 with a rated flow of 700lph, which is identical to my current filter, however it had a tiny media capacity! My current filter is a JBL Cristal Profi 250 (yes I would have liked the 500, but space and money didn't permit at the time, I operate on quite a low budget most of the time) which also has a rated flow of 700lph but I managed to fit the entire quantity of biological media from my old filter into just 1 of the 3 baskets in it!! So high flow does not always equate to large volume, especially at the lower end of the market.

My filter has absolutely great media volume, but not so great turnover, so this is where pumps/powerheads really shine! As already noticed they are considerably cheaper than larger filters, especially if you already own a filter and are looking to upgrade the flow! Now I quite happily admit that in my tank the circulation from my JBL would be nowhere near adequate, but pumps come to the rescue here! I currently have a fluval 2 (that I have owned for many years) loaded with filter wool only at the opposite end to my filter outlet, pointed towards the front glass.

I get very little algae growth, and excellent plant growth.

Oh and one thing I would say if using very large filters with high outputs, I should think that you need to make sure that this output isn't coming all from one outlet. So perhaps important to make sure that newbies don't go plonking an Fx5 on their 180 litre, and then putting jet outlets onto it! Surfs up! lol

As to aesthetics, I don't really notice my little Fluval 2 much once the plants grow in. On a more minimalist 'scape' though I can easily see why some people wouldn't want all that kit in there. As to the tren for using inline kit, sure some of the poeple are buying this for aesthetic reasons, but I would bet that an awful lot are buying it to be 'fashionable'. Planted tanks are currently all the rage, so it's only natural that this bit of the hobby will get it's fair share of 'fashion victims'.

Ade

 

[Matt Holbrook-Bull]

hehe surfs up indeed!

Im aiming to upgrade to an FX5 and rig up something to split the flow between a full lateral spray bar, and another outlet washing down the back wall, or something similar.. that way it should lesson the ferocity and provide a good mixing action, will see how it goes.

 

[Dave Spencer]

I won`t allow any hardware in to my tanks that will dictate where I have to aquascape to hide them.

When I set my tanks up intitially, I always have high light, turbo growth and be able to grow anything from an unresticted plant list in mind. With this, and the fact that I love my fast growing stems, I look to keep filter media down to a minimum and turn over to a maximum. I have never cycled a tank or witnessed any ammonia or nitrite. One thing I don`t underestimate with my turbo growth biomass is their performance in keeping the water column safe for my fish.

Using in line CO2 reactors is a pain, because I find they can restrict flow considerably. I have recently upgraded my 60l to a Tetratec 700.

Dave.

 

[Ed Seeley]

James, I remember that urea experiment you did and Barr brought up the strong possibility that the filter and sediment bacteria were reducing the ammonia in the urea via enzymatic action of urease. That would mean the bacterial reaction to NH4 is very quick, and that suppression of NH4 spikes are attributed to rapid nitrification.

I guess I also disagree with the assessment that "...tiny amounts of ammonia..." are produced in a planted tank. I would argue that the ammonia production is high and is constant simply by virtue of metabolism. Just consider the amount of ammonia generated during a tank cycling. That ammonia production rate never stops, and in fact it accelerates when we add plants and animals and food. It's just that we measure a low concentration level because the NH4/NO2 is being processed. Barr brought up the point in that thread that if you thought ammonia production in a tank was low, all you need do is to turn off your filter for a while and see the results.

As I biologist I draw the analogy to a Tropical rain forest with a healthy planted tank - Lots of nutrients locked up in the plant mass, but small amounts detectable free as the plants rapidly assimilate it. There is a distinct possibility that bacteria are outcompeted for nutrients at times by the plants assimilating the ammonia as well as the factor that other nutrients may at time limit bacterial growth such as oxygen.

All we have to do is to look at our empirical evidence. How many reports are there of algal blooms in a planted tank? Algae has become almost a central theme. A contributing factor? Ammonia production not attenuated by the available bacterial colonies. So what you say is true, that low stable levels of ammonia keep the blooms at bay but how does one achieve low stable levels? Its certainly not stable when one feeds the fish for example. Metabolic rates and organic waste decay are not really all that stable as the plants grow or are trimmed, or when water is changed. I would argue that an aquarium is the least stable aquatic environment known to man. If sintered glass media or sponges function as we think they do, by making space available for hosting bacteria, then more space means that a rise in NH4 allows these germs to increase their population more easily. If less space is available would this not affect the rate of bacterial population increase necessary to consume an NH4 spike?

I think a key factor in a lot of algae outbreaks is a lack, or reduction, of maintenance. It's easy to say that this is ammonia, but there will be lots of other organic molecules floating around too - maybe those are a trigger too/instead?

I don't really think it's the space per se that's the real benefit of sintered glass material. I think the texture allows a range of micro habitats within it that allow a wider range of microbiological life that means the filter is better equipped to deal with all sorts of changes, whether that's nutrient levels or other problems.

As to space there will be more preferable sites for certain fauna to proliferate and they will be the real estate that is in demand and therefore more highly populated. Huge amounts of media will probably be under occupied as there isn't anything for them. Whether all the nutrient is used in one pass or not really isn't the issue and wouldn't necessarily indidcate limitations as some nutrients will pass through in area without contacting the biofilm regardless of filter size.

Bacterial colonies will form a denser biofilm and this can be thicker or thinner depending on the limiting factors to bacterial growth so you only need enough space, not lots of spare space IMO.

We observe that detritus and organic waste buildup stifle a filter by blocking the pores of the media reducing the bacterial population. Detritus sitting in the filter breaks down into ammonia which fails to be processed by the colony. The result is often BGA if filter maintenance is not performed. It seems obvious to me that if you have more filter capacity to begin with the likelihood of this condition is reduced. Maintenance is still required, obviously but you have more biomedia and space to begin with so the effect is lessened and your margin of error is widened.

But isn't the same amount of detritus going in regardless? Surely the last thing you want is it sitting in a large filter producing ammonia? Best to remove it ASAP.
And why will blocked pores reduce the bacterial population? They may decrease one type but another will take over as long as areas don't become anoxic and this will only happen if the filter isn't maintained and a larger filter may lengthen this time. Surely it's better to have a smaller filter and clean it more often to remove the detritus and therefore the soruce of ammonia?

I also don't buy the assumption that bacterial populations are necessarily limited by NH4 availability. Of course this could be the case under certain conditions but we really haven't measured populations versus NH4 concentration so this would be speculative. Also it's not certain that all the NH4 in a volume of water is removed during a single pass though the filter. So if I connect two filters in series this assumption would mean that bacteria colonies would be established in the first filter and not the second. Clearly, while the available space is not completely filled in both filters the available space represents a potential that affects the speed at which the population can increase. This population agility allows absorption of ammonia spikes which occur constantly.

Again, I refer to the urea thread in which Barr referenced a list of K.R. Reddy journals. Further investigation reveals that bacteria, like plants and animals require more than just Nitrogen to prosper. They require Carbon and Phosphorus as well as other ingredients. So a bacterial population could easily be limited by the availability of other nutrients. Like Nitrogen the other nutrients must be in the right form for them to digest. Some bacterial species can obtain their nutrients in a variety of forms (i.e. organic and/or inorganic) or they can use substitute elements for their biological processes, such as Sulfur in lieu of Oxygen. Other species are less agile and suffer die off if their specific needs aren't met.

Whether it's ammonia or some other nutrient that limits the bacterial growth, it certainly can't be space in an established biofilm as the bacteria will also be colonising every other surface so why add more filter capacity?


I've been thinking long and hard about this whole idea in reference to my koi pond and trying to apply some of the ideas from there to planted tanks. While many things are different and some ideas do not translate the basic principles in both are completely sound. The biggest factor in effective biological filtration in a koi pond is not size as such but the oxygen present in the filter. The two most effective filtration methods used in new ponds tend to be either fluidised bed filters where a slightly bouyant media is kept in suspension by large quantities of air bubbling through it and a shower type filter using ceramic media where very large amounts of water at high turnover rates are chucked over the filter.

Both work well as they do a number of things;
Neither settle out any detritus in the filter (the fluidised filters need a static bed to act as a strainer and the Showers simply process the waste thanks to their special ceramic media - don't ask how!!!).
They keep large amounts of oxygen in the water to allow large amounts of aerobic respiration.
They use a relatively small amount of media but use it very effectively and produce a range of niches where different microorganisms can flourish.

When you compare the amount of waste these filters have to process compared to that in a planted tank then it's stratling to me that we worry about adding extra filters. I think if our filters' turnovers were up to the job then we wouldn't need to worry about adding anything extra.

I don't think an extra filter can possibly hurt, but I really don't think they're usually necessary either.

 

[JamieH]

I don't think an extra filter can possibly hurt, but I really don't think they're usually necessary either.

ther


There's a couple of other points though...

What of asthetics? Crystal clear water in a display tank is attractive - larger / more filters aide in this. Also, taking more particulate matter out of suspension surely helps light penetration in the tank, too.

 

[Ed Seeley]

I don't think an extra filter can possibly hurt, but I really don't think they're usually necessary either.

ther


There's a couple of other points though...

What of asthetics? Crystal clear water in a display tank is attractive - larger / more filters aide in this. Also, taking more particulate matter out of suspension surely helps light penetration in the tank, too.

But if your filter has a turnover of 4 times the tank's volume anyway then it only takes 15 minutes for all the tank's water, on average, to be passed through the filter. If your filter isn't removing fine particulate matter then the flow rate is either too high and fine particles aren't settling out in the filter or you need to use filter media that filter out smaller particles like floss or or JBL Symec Micro. You don't need huge turnovers through a filter to do that.

 

[plantbrain]

I do not think I ever told anyone to do lower flows etc in the past. I've always been a strong advocate of over filtration and higher flow rates.

It's just thinking about it in the context of CO2 and mixing and reduction of flows due to the thick plant beds as they grow and fill in a tank are newer concepts I've raised to the attention of hobbyist.
Fish can get lazy and fat, much like us if they do not swim a lot, they will eat better, behave better etc also.

Steve and George Lo at AquaForest also over filter, 20X turnover is good.
Dupla long ago suggested high good current as well.

I have not 4000 lph, rather, 3.785X that, 3000 gph.

1000gph from the Filter, 2000 from the powerhead, I have 2 of them, but then reduced it back to 1 because the plants swayed in a manner that bugged me and it was a bit too much.

I use powerheads for added flow and a nice rippling like in the ADA photo's(he just does that for effects for the photo with a hair dryer). This allows good directed flow and good surface movement with minimal eletrical cost.

Ed, I think you and the rest of the folks here are on the right track.
The NH4 is locked up in biomass and is rapidly cycled to another critters, plant, bacteria etc.

When growth wanes, then we see more NH4 backed up, we see higher CO2 and lower O2(unless low CO2 caused this, then you know and can predict the mess from there.......).

Plant cuticles are made most of esterfied C16-C18 molecules which require a lot of reduced Carbon, no carbon, plants stop making it and use the reduced carbon for more essential functions.
Algae then can easily grow on the surfaces.

"What induces algae" needs to be a focused question.
It does relate to plants etc, but keep it on it's own.

Ask yourself if you where an algae spore, what signals would allow you to grow, bloom, and repduce sexually and produce more spores for the next season?

Plants are just vegetatively growing massive weeds.
There's no sexual phase to 99.99% of folks' horticulture methods.
All clonal cuttings.

Germination occurs in algae much like plants. Temp, CO2, O2, intensity of light, duration of light, NH4, current(which relates to CO2/O2). I have not found much else.

Regards,
Tom Barr