# Oase 250 thermo filter mods



## Deano3 (11 Feb 2020)

Hi everyone i currently have a oase 250 thermo on my tank, i am going to make a few changes to my filter i am going to change pre filter sponges to maybe the carbon ones once i find out what ppi they are as want more flow and hopefully help water quality.

I am going to drill more holes on pre filter tubing maybe its only on a 45p to be honest flow isnt bad.

I want to remove some of the blue sponge and put in more biological media any recomendations ? And would this be better for the aquarium.

Thanks dean

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## Sammy Islam (11 Feb 2020)

It has 4 baskets right? So i would arrange as:
Bottom basket - blue foam
Then 2 trays of bio media
Top basket - orange foam pad with purigen underneath the foam.

Regarding the carbon prefilter foam, doesn't the carbon have a life span of a month or whatever before it stops absorbing stuff? If it was my filter i would use the course prefilter foam and then a bag of carbon with the purigen which would sit under the orange foam in the top basket.


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## Deano3 (11 Feb 2020)

Sammy Islam said:


> It has 4 baskets right? So i would arrange as:
> Bottom basket - blue foam
> Then 2 trays of bio media
> Top basket - orange foam pad with purigen underneath the foam.
> ...


Thanks sammy i agree, i have seen videos were they cut one of the origional blue sponges to size for pre filter so i will do that.

What bio media would you recomend and purigen ?

Do you think will help and be good for the aquarium ? As i dont really know the science behind what differnce it will make

Thanks dean

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## Sammy Islam (11 Feb 2020)

Yeah you can cut your own foams from the blue ones supplied. But i would still have one blue sponge in bottom basket.

Theres lot's of bio media available, i use seachem matrix and have used the fluval ceramic tube like things before. I don't think it matters really as they all do the same job and in a planted tank the plants will do most of the filtration for you if they are healthy etc.


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## Deano3 (12 Feb 2020)

Sammy Islam said:


> Yeah you can cut your own foams from the blue ones supplied. But i would still have one blue sponge in bottom basket.
> 
> Theres lot's of bio media available, i use seachem matrix and have used the fluval ceramic tube like things before. I don't think it matters really as they all do the same job and in a planted tank the plants will do most of the filtration for you if they are healthy etc.


Just got email back from oase and carbon filters are 60ppi so far to fine for pre filter. 

If someone can tell me the benefits of having more biological filtration that would be great.

Think i will do what you suggest cut one blue sponge for pre filter then have one blue sponge at bottom then 2 trays of bio then the orange sponge.

Thunk i may also drill a few more holes in the pre fikter tubing.

Thanks dean


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## dw1305 (12 Feb 2020)

Hi all, 





Deano3 said:


> If someone can tell me the benefits of having more biological filtration that would be great.


The issue is really to do with ammonia (NH3/NH4+). Ammonia is produced by all aquatic multi-cellular animals (fish, shrimps, snails etc.) following the digestion of proteins. <"Any excess of amino acids"> are deaminated to form ammonia, which continually diffuses from the fish and shrimps gills into the water column. 

<"Ammonia is toxic"> at fairly low levels (well below 0.5ppm) so it is important that that ammonia is converted to the equally <"toxic nitrite (NO2-)"> and relatively <"benign nitrate (NO3-)">. 

*We need to remove the ammonia and nitrite as rapidly as possible, we can't allow their levels to build up.* 

It is different for the NO3, we are only going to get toxicity when we are into the hundreds of milligrams per litre (mg/L = ppm).

Nitrification is an oxygen intensive process and also reduces water hardness (acids are "H+ ion donors", and we've added three of them). 

*Non-planted tank*
In an aquarium without plants biological nitrification is the process where a <"specialised range of micro-organisms"> (mainly in the filter) convert NH3/NH4+ to NO3-, either via NO2-, or in the case of _Nitrospira _ <"directly from NH3 to NO3-">. 

This is where a lot of the discussion in forums etc gets side-tracked, because it looks on 

ammonia and 
the nature, and volume, of the biological filter media
as the important issues, where it *should be looking at oxygen*. *Microbial biological filtration is <"nearly always limited by oxygen availability">. *


dw1305 said:


> Sellers of Matrix, Biohome etc. will tell you that you can have <"simultaneous aerobic nitrification and anaerobic denitrification"> in the same media, with a steep oxygen gradient across a small spatial separation. There are a number of reasons why this isn't a good idea, the primary one would be that you are always teetering on the brink of low oxygen levels, leading to incomplete nitrification, which leads to <"ammonia and/or nitrite levels rising and killing all your fish">.


Assuming we have sufficient oxygen, NO3- will accumulate in the water column, and can only be removed by anion exchange, dilution or <"anaerobic denitrification"> (the linked <"Media set up"> thread has a lot more detail).  




 

*Planted Tank*
The schematic below for photosynthesis is the most important equation for (multicellular) life on earth and gave us the oxygen we breathe


 
A planted aquarium increase <"the potential for nitrification"> in three ways:

Plants directly take up all <"forms of fixed nitrogen">.
They are <"massively net oxygen producers">.
They greatly <"increase the area where microbial nitrification can occur">. 
Compared to using plants, attempting anaerobic denitrification in a canister filter is such a bad idea, I can't actually imagine why any-one would advocate it as a viable option. There is a fuller discussion in the PlanetCatfish <"Using deep gravel....."> thread, where not every-one is a planted tank keeper, and it dips in and out of various UKAPS threads.

cheers Darrel


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## Deano3 (14 Feb 2020)

dw1305 said:


> Hi all, The issue is really to do with ammonia (NH3/NH4+). Ammonia is produced by all aquatic multi-cellular animals (fish, shrimps, snails etc.) following the digestion of proteins. <"Any excess of amino acids"> are deaminated to form ammonia, which continually diffuses from the fish and shrimps gills into the water column.
> 
> <"Ammonia is toxic"> at fairly low levels (well below 0.5ppm) so it is important that that ammonia is converted to the equally <"toxic nitrite (NO2-)"> and relatively <"benign nitrate (NO3-)">.
> 
> ...


Wow darrel thats a lot to take on and get my head around so thanks for taking time to respond like that.

I understand the purpose of the filter is to oxygenated the water and get as much of the ammonia and nitrites out of the water colum and turn into the less harmful nitrate.

I also get that the plants have a large part in this process by taking in ammonia and giving out oxygen and also the beneficial bacteria can be on the plants converting the bad bacteria into nitrates but at the end i am not quite sure what you mean about anaerobic dentrification and you say its not a good thing ? 

Sorry of sillily question, so would advise adding some more biologoical filtration into the cannister ?

Thanks again
Dean

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## dw1305 (14 Feb 2020)

Hi all,





Deano3 said:


> Wow darrel thats a lot to take on and get my head around..........at the end i am not quite sure what you mean about anaerobic dentrification and you say its not a good.


It is a lot to get your head around, but it is really important.

Anaerobic denitrification is fine when it happens in the substrate. The problem occurs in the filter, you need to carefully balance the oxygen budget so that you have simultaneous aerobic and anaerobic processes. The issue is that you are balanced on knives edge between having enough oxygen and not having enough.

Not having enough oxygen is a disaster, because you end with levels of ammonia and NO2- rising, with inevitably fatal results for your fish.

If you have an excess of oxygen you don’t get the conversion of NO3 to N2 gas, but if you end up with more ammonia in your tank it is converted to NO3 and your fish live.

That is why it is so important.

Cheers Darrel


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## jaypeecee (25 Apr 2020)

Hi Folks,

Just caught up with this thread!

I have made numerous dissolved oxygen measurements on my tank. And I've done these measurements at different times throughout the day. What I have found is that oxygen concentration is always around 8 ppm, which is the maximum oxygen concentration that fresh water (not marine) can hold at tropical tank temperatures. And, this is even when those dreaded films build up on the water surface. I simply position the external filter outlet pipe in such a way that the water flow 'breaks' the surface. I also use CO2 injection.

I'd like to just add to what @dw1305 says above and that is to stress the importance of reducing organic waste in the tank as this increases BOD*. This means clearing out 'crud' that builds up in the filter and ensuring that detritus is not allowed to build up on the substrate. When 'crud' builds up inside the filter, not only does it increase BOD* but it also reduces flow rate which, in turn, potentially reduces oxygen concentration. A 'double whammy' of the worst kind!

*BOD = biological oxygen demand

JPC


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## Richard40 (25 Apr 2020)

Ive just changed my Oase 250. I’ve put coarse filter sponges in the pre filter. Then I’ve a medium sponge and fine sponge above in the first basket. Second basket I have Aquario Neo soft, one litre’s worth. Third basket a bag of Purigen and last the final sponge.


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## dw1305 (26 Apr 2020)

Hi all,





jaypeecee said:


> What I have found is that oxygen concentration is always around 8 ppm, which is the maximum oxygen concentration that fresh water (not marine) can hold at tropical tank temperatures.


You would really need to find out what the oxygen level is just before the lights come on (and the room is dark) to find the lowest level of DO.  People have often said to me "_plants use oxygen at night, _and I tell then that this is true, but when you enter night in a <"planted tank you have much higher levels of dissolved oxygen"> than you would without plants.

If you don't have plants your tank it is <"_always night">._

Other than that "_yes_" it is <"DO levels are always about 8 mg/L"> and that is the saturation value at about 25oC.





To use the chart you draw a straight line between water temperature and "oxygen.ppm", and % saturation is where it crosses the central (diagonal) axis. It doesn't take atmospheric pressure or salinity into account, but they are very minor adjustments unless you keep marines or live in Denver.

cheers Darrel


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## jaypeecee (26 Apr 2020)

dw1305 said:


> You would really need to find out what the oxygen level is just before the lights come on (and the room is dark) to find the lowest level of DO.



Hi Darrel,


jaypeecee said:


> I've done these measurements at different times throughout the day.



Perhaps I should have been more specific above. The different times included 'before lights on'/minimal room lighting.

JPC


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## dw1305 (26 Apr 2020)

Hi all,





jaypeecee said:


> I simply position the external filter outlet pipe in such a way that the water flow 'breaks' the surface.





jaypeecee said:


> The different times included 'before lights on'/minimal room lighting.


I'm not surprised, if you have a large gas exchange surface and plants then that is going to give you a higher dissolved oxygen levels.

That is the great thing about planted tanks, they really are the gift that keeps giving.

cheers Darrel


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## rubadudbdub (26 Apr 2020)

To answer your Q, will more biological filtration be of benefit, I'd say just use what it came with and spend more money on plants. 

I've got this biomaster 250.  I've:
Drilled extra holes in the pre filter bar  - not convinced it did much
Chopped up the coarse blue foam to make some coarse prefilters instead of the fine ones in the box. Flow seemed a little better.  
Blue sponge in the bottom tray, orange sponge in the thin top tray, same as oase suggested.
Instead of the white plastic media (K1?) I used eheim ehfisubstrat, purely because it was from a running tank. If I was setting it up from scratch I'd just use the k1 it came with.  

However, It'll work as oase intended just fine.  Plants themselves and the microenvironment will help with filtration. I never use carbon or purigen, but I only run low tech tanks.


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## Noob-dude-scaper (30 May 2020)

Oase gave us one of the best and easiest pre-filters to service.
Running course foam in the PF then medium and fine foams in the cannister housing will only create more work for yourselves by having the break the cannister down to clean out the foams.

I run the 60ppi PF`s as mechanical filtration and fill my cannister up with as much bio media i can get away with,yes the pre-filter needs a rinse once a week,i do mine with the water change but the great thing is i only ever pull out the cannister every two months or so to rinse the bio media.

Ive never had to run filter floss as the 60ppi foams remove most particles.

Ive also tried enlarging the existing holes in the pre-filter tube but it didnt make that much,if any difference,i found adding more smaller holes all around gave me slightly more flow.


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## rubadudbdub (30 May 2020)

Noob-dude-scaper said:


> Running course foam in the PF then medium and fine foams in the cannister housing will only create more work for yourselves by having the break the cannister down to clean out the foams.



I agree.  Having previously used a coarse prefilter to get more flow, I've gone back to the fine ones originally supplied.   The bottleneck became the fine orange foam in the top level of the cannister necessitating cleaning.   Flow isnt (subjectively) noticeably different.


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## mourip (11 Jun 2020)

As I am laboring over how to set up the chambers on my 250 I thought that I would add this piece of information.

Most here already know the Oase  *prefilter sponges* are color coded.

Black 60ppi
*Blue 45ppi*
Orange 30ppi

The above is correct for the pre-filter sponges.

...but Oase lists the *Blue tray pad as 20ppi*

So much for color coding! A bit confusing for those of us trying to dial it in...


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