# surface scum



## Keith (5 Sep 2007)

My 6' low tech planted tank has been set up for eight weeks now and in the last week it has started to develop a brown surface scum that keeps building up. Today I cleared it by floating newspaper but by this evening it was coming back again.

I am using a Tetratec Ex 1200 cannister filter and noticed that the minimal surface current was not reaching the end of the tank so I removed a mass of Hornwort and cut back the giant Vallis leaves. 

The problem seemed to start when I introduced 20 Cherry red Shrimps and put a large sponge filter over the end to stop them disappearing into the filter.

Am I right in thinking that increasing surface flow would be counter productive in a low tec tank? Also adding Mollies would probably be the end of the shrimp?

I am going away shortly and really need to sort this out quickly as I cannot ask my fish sitter to float newspaper every couple of days.

So far I have not done any water changes but would do so if you think it would help.


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## James Flexton (6 Sep 2007)

Hi Keith,

my first thought when i saw the topic heading was surface agitation so that would be my first point of attention. i would not over do it however as you will drive off co2 which will already be in short supply in a low tech tank. as long as the water has ripples reaching the four corners that should be enough. dont let the filter outflow break the surface. 

how often do you do water changes on the tank? that may be an issue. definatly do at least a 20% water change that should clear it up but wont solve the original cause which you will have to get to the bottom of or it will just come back.

what are your water stats out of interest?

if i were you i would not use newspaper as i'm sure it contains all sorts of chemical nasties not to mention ink. in a low tech tank where your water is sitting there unchanged for a long time the toxins will build up each time you do it. i cant back this up with any specific problems i know of but it cant be good IMO. 
paper towel will do a better job i've used this before to good effect. tesco value has a use somewhere.....


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## ceg4048 (6 Sep 2007)

Hi Keith,
              Another possibility; from what I've seen is that surface scum is often an indication of stressed plants leaching proteins back into the water column. My first inclination is to increase nutrient dosing first before I try making adjustments to anything else.

Surface scum seems to be controversial issue so I'll just say that when I see scum I add a bit more of every nutrient and it normally goes away. I have to qualify this though  in that that's always been the case in my high tech tanks. I can only extrapolate this to low tech setups, but scum is scum and it can only be coming from the plants. If so I reckon it can only be because they are unhappy. As bizarre as it may sound I normally equate surface scum with starvation.


Cheers,


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## Keith (6 Sep 2007)

Thanks for the replies.

Firstly I have to say that there are very few ripples on the surface and these are confined to one side only. Could this be the reason that the opposite end sees the greatest build up of scum? Anyway I will adjust the filter outflow accordingly.

Secondly water changes. I have not done any yet and did not intend to do any unless I have a major upheaval of the substrate.

 I don't use a dechlorinator I just let the tap water stand for 24 hours.

Water stats:-   Tank No3  0  Stored water 0
                                No2  0                         0      
                                GH  17                        17
                                dKH 17                       17
                                pH   8.4                      7.8

I take the point about newspaper and should have thought of it myself - thank you.

The point about stressed plants is very interesting as there is no nitrate reading from the water although I dose 1/8 tsp per 20 gallons. I also dose 1/32 tsp PO4 per 20 gallons and 1/4 tsp Equilibrium per 20 gallons. This is as recommended in the Barr Report on Non CO2 systems. I rather like the pink tinge to the leaves on my Hygrophila polysperma and then read the other day that this is due to a lack of nitrate so this fits in with the stressed plants idea. Do you think I should double the addition of both NO3 and PO4 to keep them in balance or just increase the nitrate?

Thanks in advance.


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## beeky (6 Sep 2007)

I had pink tinges to the edges of the leaves on my H. polysperma at the top of the plant and I had quite high nitrate. I put it down to the greater quantity of light reaching those leaves.


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## Keith (6 Sep 2007)

Yes coming from a reef tank environment that was my first reaction until the leaves on those plants I was trying to dwarf at the front of the tank, and one of those was only 1 1/2" tall, also turned pink.


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## Dan Crawford (6 Sep 2007)

You could use "news print" (chip shop paper) for the surface scum but i would reccomend a good quality kitchen towel like "bounce" or somthing, NOT the cheap ones coz they can break up pretty quick and you don't want to be trying to sift out tiny bits of paper wizzing around your tank.  
Obviously it is better to get the bottom of the issue though.
HTH
Dan


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## ceg4048 (6 Sep 2007)

Keith said:
			
		

> Thanks for the replies.
> 
> 
> The point about stressed plants is very interesting as there is no nitrate reading from the water although I dose 1/8 tsp per 20 gallons. I also dose 1/32 tsp PO4 per 20 gallons and 1/4 tsp Equilibrium per 20 gallons. This is as recommended in the Barr Report on Non CO2 systems. I rather like the pink tinge to the leaves on my Hygrophila polysperma and then read the other day that this is due to a lack of nitrate so this fits in with the stressed plants idea. Do you think I should double the addition of both NO3 and PO4 to keep them in balance or just increase the nitrate?
> ...



Hi Keith,
              That pink tinge is so difficult to pin down. I use massive quantities of NO3 and still get the tinge, but only on a small percentage of leaves. I love red but I don't want pay the consequence if I scew up. I'm never afraid to double my dosage of everything because Barr has convinced me that light, ammonia and unstable CO2 are the only algae causal factors. Remember that you can always back down bit by bit until you get the desired effects but if you are underdosing you have nothing but headaches. It might take a leap of faith but I would double NO3, PO4 and micros. Remember also that we really don't care about NO3/PO4 ratios, we just care that we are not limiting either. My opinion is that the term "balance" is overused and in a sense, irrelevant since it _implies_ some kind of standard ratio. As long as we know that we have more than enough of each nutrient then we needn't ever worry about actual values or actual ratio of values. I find the concept totally liberating. 

By the way, I doubt that you have zero nitrate if you are just reading from an uncalibrated test kit.

Cheers,


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## Keith (6 Sep 2007)

"As long as we know that we have more than enough of each nutrient then we needn't ever worry about actual values or actual ratio of values. I find the concept totally liberating. "

Isn't it just!!

I have altered the angle of my filter output to increase the surface ripples and it seems to be working. The scum was broken up and now seems to be disappearing. It does of course beg the question of the cause so after giving it 24 hours I will then double my dosing..

Thanks


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## beeky (7 Sep 2007)

Could you get some and have a look under a microscope?


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## Keith (9 Sep 2007)

Well I don't know what has happened to my posts for this thread but two seem to have gone walkies.

I don't have access to a microscope I am afraid.

Increasing the ripples helped break up the scum and then yesterday I added my usual ferts and followed up with a second dose today and the scum has gone.

Its early days yet but I will add ferts twice a week and keep hoping.

Thanks for the suggestion.


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